T****n
发帖数: 6187 | 1 staples的deal，第一台HP$250，Acer$300。HP应该更好些，但是担心n3530会不会太慢
。另外touchscreen实际使用上有多大好处？多谢了
1) HP 15-r063nr [staples.com] - In ad for $349 (originally $499). Should be
$249 after coupon
Intel® Pentium® N3530 Processor
4GB DDR3L SDRAM, 500GB 5400RPM hard drive
15.6-inch diagonal HD BrightView WLED-backlit touchscreen display (
1366x768)
1 x USB 3.0 port and 2 x USB 2.0 ports
1x1 802.11b/g/n WLAN
Windows 8.1
2)Toshiba C55-B5272 [staples.com] In ad for $399 AR ($549 origin... 阅读全帖 |
|
w****g
发帖数: 44 | 2 1. Write a Java method that, given a square matrix of integers, returns
true if there is at least one row, column, or diagonal that is all zero. The
signature should be:
class MatrixZeroTest {
enum TestType { Row, Column, Diagonal }
public static boolean allZeros(int[][] matrix, TestType type);
} |
|
t********n
发帖数: 611 | 3 Can't run this Gauss elimination program. Got error message : not enough
input arguments.
function x = gauss(A,B)
%The sizes of matrices A,B are supposed to be NA x NA and NA x NB.
%This function solves Ax = B by Gauss elimination algorithm.
NA = size(A,2); [NB1,NB] = size(B);
if NB1 ~= NA, error(’A and B must have compatible dimensions’); end
N = NA + NB; AB = [A(1:NA,1:NA) B(1:NA,1:NB)]; % Augmented matrix
epss = eps*ones(NA,1);
for k = 1:NA
%Scaled Partial Pivoting at AB(k,k) by Eq.(2.2.... 阅读全帖 |
|
k*****6
发帖数: 26 | 4 有python比较熟练的朋友帮忙看下这两道题吗？万分感激。。
Do both of these problems using at least one loop each and not using any
special pre-existing functions that give you the answer with just one line
of code.
1. Make a function to count the number of times a specified number is
repeated in a list/array. That means that if we have a number list
numberList=[5, 12, 0, 7, 2, 5, 10, 9, 12, 5];
and we use the function call
numRepeats(numberList, 5)
we get the output: 3 --- meaning 5 occurs three times in numberList.... 阅读全帖 |
|
f*r
发帖数: 3968 | 5
不就是个箱子么，不必然需要 :)
看情况了，ST80是短焦距镜，焦距才400mm,
也就是说用26mm目镜的放大率才15倍，用10mm目镜的放大率才40倍
实际上是介于一般双筒镜和一般望远镜的放大倍率之间的一种广角镜子
用来看银河啦七姐妹星团啦英仙座双星团之类的固然很爽
可是40倍的放大率看土星连土星环都看不太见的
Barlow就是增倍镜，和10mm目镜合用放大倍率就成了80倍了
80mm的镜子，极限可用放大率也就是150倍的样子
Orion的这个Shorty Barlow声誉倒是很好的
最外面的两面是多重镀膜的，现在也正在Sale, $40降到了$30
倒是很划算的
但是要注意，这个镜子焦比只有5, 本就不是很适合看行星的镜子
还有Prism Star Diagonal.
这个不一定需要罢，ST80自己带个45度角的正像Prism Star Diagonal
可以看 |
|
t******t
发帖数: 13 | 6 这里牛牛多,问个问题.
我有一个阶数很大的BLOCK TRIDIAGONAL矩阵(暂称为D)
每个BLOCK又是TRIDIAGONAL的
按照LAPACK所需的格式我知道怎么压D
问题是等我压完了,猛一抬头看我算法里
实际需要的是 D*D
而这个好象是BLOCK PENTA-DIAGONAL的矩阵
每个BLOCK又是PENTA-DIAGONAL的
哪位有什么好的resource来压这个么?
多谢. |
|
g***i
发帖数: 90 | 7 ( M+\delta K ) V = M V \Lambda
here \Lambda is the diagonal matrix with
diagonal entries to be the eigenvalues
so
M V \Lambda V' = M+\delta K
...
may or may not work. pls check |
|
g***i
发帖数: 90 | 8 given the hilbert matrix (1/(i+j-1))_{i,j} with large
dimension, prove that every of it's off-diagonal
block has small numerical ranks.
this is kind of unclear. but if u do some numerical
experiments, you can see, for the 100x100 hilbert
matrix, the off-diagonal blocks have numerical rank
almost < 10.
one idea is to use taylor. |
|
k*****6
发帖数: 26 | 9 有python比较熟练的朋友帮忙看下这两道题吗？万分感激。。
Do both of these problems using at least one loop each and not using any
special pre-existing functions that give you the answer with just one line
of code.
1. Make a function to count the number of times a specified number is
repeated in a list/array. That means that if we have a number list
numberList=[5, 12, 0, 7, 2, 5, 10, 9, 12, 5];
and we use the function call
numRepeats(numberList, 5)
we get the output: 3 --- meaning 5 occurs three times in numberList.... 阅读全帖 |
|
x*****d
发帖数: 427 | 10 发信人: cheeryyu (浪人清歌), 信区: Mathematics
标 题: [转载] How to calculate det(A)???
发信站: The unknown SPACE (Thu May 29 20:53:48 2003), WWW转贴
【 以下文字转载自 EE 讨论区,原文如下 】
发信人: cheeryyu (浪人清歌), 信区: EE
标 题: How to calculate det(A)???
发信站: The unknown SPACE (Thu May 29 20:26:04 2003) WWW-POST
A is a Hermitian matrix with complex values, all the diagonal values equals to
1, and the norm of all the off-diagonal values are less than 1.
Now I guess det(A) <= 1? that is, the product of all the eigenvalues are less |
|
a***s
发帖数: 103 | 11 如果矩阵H可以表示成：
H=D*A+A^T*A
其中，
D是diagonal matrix, diagonal elements positive，
A是正的square matrix，就是所有的elements都positive。
在D,A满足什么条件时，能保证H矩阵positive definite吗？
谢谢～ |
|
w**a
发帖数: 1024 | 12 let vector v=[x(t) y(t)]', ' is transpose
A=[a b]
[c d]; assume a,b,c,d are const.
dv/dt = A *v
you can do a coordinate rotation then diagonalize matrix A.
let C be a coordinate transformation matrix
(1) dv/dt = A*C'*C*v
multiply (1) by C
(2)d(C*v) = C*A*C'*(C*v)
let vector u = C*v and matrix E = C*A*C', because E is diagonal matrix,
E11 = e1; E12=E21=0; E22 = e2;
(3) then we have,
du1/dt = e1*u1
du2/dt = e2*u2
the solution is obvious now.
bifurcation might occur. |
|
s**c
发帖数: 1247 | 13 A,B n*n，symmetric, AB=BA,A的eigenvalue的multiplicity都是1
求证：A,B能simultaneously diagonalized
i.e. 存在orthogonal的矩阵P，A=PDP',B=PEP',D,E是diagonal的矩阵
3x |
|
q**j
发帖数: 10612 | 14 打算把一个positive definite, symmetric 的矩阵分解成两个矩阵， i.e.，
A = B*B.
按照原理可以用eigen decomposition 把A分成 V*D*V^(-1)。其中D是diagonal的。因为
A是正定的所以D的对角线上面都是正数。所以定义E是D的平方根，
A= V*D*V(-1) = V*E*E*V(-1) = V*E*V(-1) * V*E*V(-1)，所以定义
B = V*E*V(-1)，就可以有A = B*B。
可是在matlab里面用了 [V,D]=eig(A)以后，出来的D不是diagonal的。应该是计算精度
的问题吧。这下怎么办？有没有好办法来对付这个问题？多谢了。 |
|
N***m
发帖数: 4460 | 15 If D is not diagonal, then set it to diagonal.
因为 |
|
s****z
发帖数: 141 | 16 都是2＊2的矩阵，A，B，C，D 已知，求X
A * X * B ＝ diagonal matrix
C * X * D ＝ diagonal matrix
能求得唯一解X吗？
多谢！ |
|
h********2
发帖数: 23 | 17 ☆─────────────────────────────────────☆
Question 5.
A n*m matrix is composed of n*m unit cubes. Draw a diagonal line connecting
two opposite corners of matrix, develop a formula showing how many cubes are
crossed(touch on corner does not count as cross) by the diagonal line are
any n and m.
A: n+m-gcf(n,m), with gcf the greatest common factor. |
|
b***k
发帖数: 2673 | 18 ☆─────────────────────────────────────☆
ilovelg (nothing) 于 (Mon Feb 18 12:39:23 2008) 提到:
Seeing for discussion for the following problems (some of appeared in old
posts):
1. A n*m matrix is composed of n*m unit cubes. Draw a diagonal line
connecting two opposite corners of matrix, develop a formula showing how many cubes are
crossed(touch on corner does not count as cross) by the diagonal line.
Answer is n+m-gcf(n,m). why?
2. Russian roulette problem played by two people with a revolver |
|
b***k
发帖数: 2673 | 19 ☆─────────────────────────────────────☆
wealdg (wwwnet) 于 (Wed Aug 6 18:00:08 2008) 提到:
1. Write a Java method that, given a square matrix of integers, returns
true if there is at least one row, column, or diagonal that is all zero. The
signature should be:
class MatrixZeroTest {
enum TestType { Row, Column, Diagonal }
public static boolean allZeros(int[][] matrix, TestType type);
}
☆─────────────────────────────────────☆
snnn (snnn) 于 (Wed Aug 6 21:52:59 20 |
|
g********t
发帖数: 11 | 20 1: not always can be filled by "L". e.g. if the total # of cells is not
divided by three.
another example: for 8 X 8 chess board with cell (i,j) 1<=i,j<=8, there are
54 cells with index other than (3,1~2) or (2,1~8). However, these 54 cells
can not be filled by "L".
The above divide and conquer (from size 2^n to size 2^(n-1)) may not work
either if the division makes one of the quarter can not be filled by "L".
请问高手，有没有好的办法判断哪些情况可以被"L"覆盖， 怎样去覆盖？
2: repeat the following steps and stop at any time... 阅读全帖 |
|
a**m
发帖数: 102 | 21 first consider the case that gcd(m,n)=1:
Suppose n>=m, consider the intersections of the diagonal and the horizontal
lines, their coordinates are 0, m/n, 2m/n, ...,nm/n(=m).
if the open interval ((k-1)m/n, km/n) contains an integer, this means the
diagonal crosses 2 squares in the k-th row, otherwise it crosses only 1
square.
Note that the open interval can contain as many as one integer because n>=m.
We know that 1,2,...,m-1 will appear in some of the n open intervals, so
there are m-1 open int |
|
i**w
发帖数: 71 | 22 这些是最近两个月每次面试完，给C同学(谢谢陪我一路哈~~)的汇报整理出来的。其实
也没怎么整
理...
大部分都是常见的题。有些常见的题就直接没列。还有些当时忘了的，现在更记不起来
了。
有些是电话上的，有些是onsite。题目有些没说清楚，大家将就，领会精神。
本来什么都没定下来的时候一肚子感想和经验，想着有一天搞定了，一定好好总结总结
。现在定下来
了，倒没了兴致了。。。但想想从版上看过那么多面试题和面经，我争取写点儿，励志
型的，给出身
不好的同学们一点鼓励。也顺便攒攒人品，希望OPT快点儿下来!
1. Singly linked list, write a function to print the nodes backwards.
2. solve dS = (a - b*S)dt+sigma*dW Calculate the variance of S(T)
3. what does it look like if we plot: floating variable against the
actual value assigned to the variable?
4.... 阅读全帖 |
|
i**w
发帖数: 71 | 23 这些是最近两个月每次面试完，给C同学(谢谢陪我一路哈~~)的汇报整理出来的。其实
也没怎么整
理...
大部分都是常见的题。有些常见的题就直接没列。还有些当时忘了的，现在更记不起来
了。
有些是电话上的，有些是onsite。题目有些没说清楚，大家将就，领会精神。
本来什么都没定下来的时候一肚子感想和经验，想着有一天搞定了，一定好好总结总结
。现在定下来
了，倒没了兴致了。。。但想想从版上看过那么多面试题和面经，我争取写点儿，励志
型的，给出身
不好的同学们一点鼓励。也顺便攒攒人品，希望OPT快点儿下来!
1. Singly linked list, write a function to print the nodes backwards.
2. solve dS = (a - b*S)dt+sigma*dW Calculate the variance of S(T)
3. what does it look like if we plot: floating variable against the
actual value assigned to the variable?
4.... 阅读全帖 |
|
l*****y
发帖数: 56 | 24 41. Given the N stocks returns and the covariance matrix, where the
diagonal terms are sigma1^2,...,sigmaN^2. Now we have implied
volatility for each of the stock. How to perturb the covariance matrix
such that the diagonal terms are the implied volatility, while keeping it
semi-definitive? What if we'd like to do the same, except now we'd also
like to make the new matrix satisfying: w_transpose*New Matrix*w = a fix
number, where w is a vector of fixed weights.
最初的covariance matrix的对角线是histori... 阅读全帖 |
|
z****g
发帖数: 1978 | 25 It has nothing to do with relationship between implied vol and
historical
vol. Just from pure math point of view.
1. You should know the fact: left matrix multiplication is row operation
and
right matrix multiplication is column operation. In order to keep the
transformed matrix B symmetric, you have to do transformation like
X^tAX.
Suppose the implied vol is s_1^2...s_n^2. I think the simplest answer
would
be X = diag(s_1/sigma_1,...,s_n/sigma_n). Since det(X) > 0, and B is
still
symmetric, B w... 阅读全帖 |
|
l******i
发帖数: 1404 | 26 第一题我也是3/32，有什么问题吗？
第二题是绿皮书63页原题：N points on a circle
3/4
第三题有这个定理吗？
Given matrix A, then A is a correlation matrix if and only if A is
symmetric
positive semi-definite.
我知道correlation matrix must be symmetric positive semi-definite.
但是反过来也成立吗？够充分吗？
另外： A is symmetric, diagonal dominant and has positive diagonal
elements
then A is symmetric positive semi-definite.
这样可知r=-1/3可以使A positive semi-definite.
但怎么证明-1/3就是minimum呢？条件会不会太强了呢？
第四题是绿皮书103页C题的变形。
P(B_1>0,B_2<0)=P(B1>0)P(B2-B1<0)P(|B2-B1|>|B1|... 阅读全帖 |
|
m******a
发帖数: 9 | 27 对角线是指 main diagonal 还是包括 anti diagonal? |
|
b***k
发帖数: 2673 | 28 If D is a diagonal square matrix with real values as diagonal elements.
U*D=D*U,
what kind of property can be inferred for the square matrix U? |
|
h***t
发帖数: 2540 | 29 eigenvalues of A are all greater than B if diagonalized,
so eigenvalues of B inverse are all greater than eigenvalues of A if
diagonalized.
so it is pd |
|
s*********t
发帖数: 3 | 30 在linear mixed model里，fixed effect和 random effect之间的确没有covariance。
（因为Fisher Information Matrix的off-diagonal block matrix=0） 但是在
Generalized Linear Mixed Models里，fixed effect和 random effect之间是有
covariance。（因为Fisher Information Matrix的off-diagonal block matrix !=0） |
|
e*******e
发帖数: 1144 | 31 X is an n*p matrix with n observations and p variables, \beta is the p*1 vector for a regression model, and then Y = X \beta is the n*1 prediction vector.
My question:
Define diag(\beta) as the p*p diagonal matrix whose diagonal elements are \beta, then is there a name for the quantity: X diag(\beta)? Note that this quantity is a n*p matrix, where each column is basically "the prediction values from one dimension of \beta".
Thanks! |
|
D**u
发帖数: 288 | 32 matrix 是square的？nonzero 多不多？是不是sparse的？
anyway, 可以考虑Partial SVD + Lanczos diagonalization。
简单说：
Partial SVD 是用k dimension 去 approximate n dimesion （k
后类似 cross validation 看看是不是converge。
具体对每个k dimension的用Lanczos就是一个block接一个block的diagonalization，
然后算eigen value。
相同道理，类似的方法也有不少，不过不知道是不是你想要的答案
这些都是可以stream line的， 程序写起来很麻烦，不过如果用R早就有人package好了
。强烈推荐
R 的 irlba package参见
http://cran.r-project.org/web/packages/irlba/vignettes/irlba.pd
可以跟bigmemory package 一起用，100GB data no problem。 |
|
k*****6
发帖数: 26 | 33 有python比较熟练的朋友帮忙看下这两道题吗？万分感激。。
Do both of these problems using at least one loop each and not using any
special pre-existing functions that give you the answer with just one line
of code.
1. Make a function to count the number of times a specified number is
repeated in a list/array. That means that if we have a number list
numberList=[5, 12, 0, 7, 2, 5, 10, 9, 12, 5];
and we use the function call
numRepeats(numberList, 5)
we get the output: 3 --- meaning 5 occurs three times in numberList.... 阅读全帖 |
|
t****u
发帖数: 709 | 34 numberList=[5, 12, 0, 7, 2, 5, 10, 9, 12, 5]
def numRepeats(numberList, number):
return map(str, numberList).count(str(number))
print numRepeats(numberList, 5)
第一个一行就足够了
def diagonal(multiArray):
nrow = len(multiArray)
diagonalList = []
for i in xrange(nrow):
diagonalList.append(multiArray[i][i])
return diagonalList
print diagonal(multiArray)
对空 multiArray 也一样 没问题. |
|
c******e
发帖数: 60 | 35 关于对角线换挡的方法，参见turnfast site:
When shifting across the H such as between 2nd and 3rd gears, do not try to
make a conscious jog in your hand movements. The linkage needs very little
input to make the diagonal path across neutral. Your shift should almost
look like a straight diagonal line. Making a distinctive zig zag through
neutral is strong-arming the shifter and will slow the shift down.
如果意向就是空挡，另说啦。 |
|
c******e
发帖数: 60 | 36 关于对角线换挡的方法，参见turnfast site:
When shifting across the H such as between 2nd and 3rd gears, do not try to
make a conscious jog in your hand movements. The linkage needs very little
input to make the diagonal path across neutral. Your shift should almost
look like a straight diagonal line. Making a distinctive zig zag through
neutral is strong-arming the shifter and will slow the shift down.
如果意向就是空挡，另说啦。 |
|
w*******y
发帖数: 60932 | 37 What's Included
* Westinghouse 32" Class / 720p / 60Hz / LCD HDTV
* Stand
* Remote with 2 AAA batteries
* 6' AC power cord
* Owner's manual
Product Features
* 31-1/2" screen measured diagonally from corner to corner
For optimal viewing in medium-size rooms.
* Ultraslim design (4-3/8" deep)
Comes with a table stand or can be mounted on a wall (with optional
mounting kit, not included). 200mm x 400mm VESA compatible.
* Incredible contrast ratio (2600:1)
... 阅读全帖 |
|
w*******y
发帖数: 60932 | 38 plus $14 shipping and tax
Link:
http://www.cdw.com/shop/products/default.aspx?EDC=2170703
Specifications are provided by the manufacturer. Refer to the manufacturer
for an explanation of the print speed and other ratings.
Processor
64-bit Computing: Yes
Clock Speed: 2.8 GHz
Features: Intel 64 Technology , Intel Dynamic Acceleration ,
Intel Trusted Execution Technology , Intel Virtualization Technology
Manufac... 阅读全帖 |
|
|
w*******y
发帖数: 60932 | 40 This HP dv6t/dv7t Sandy Bridge Quad Edition deal with Blu-ray Player & 8 Gb
Ram: $1,299.99 - $150 instant rebate - $200 coupon code = varies aournd $949
with FREE shipping & 2-year warranty.
Additional $200 off customized hp Pavilion Laptop on $1299+, limit 1160 uses
at hp "NB5321" applies to both the dv6tQE (15 inch model with optional
back lit keyboard) or the dv7tQE. Just be sure to be in the HP Home site and
not the EPP/Student sites.
Here are my recommended setups:
HP Pavilion dv7t Quad Ed... 阅读全帖 |
|
w*******y
发帖数: 60932 | 41 Graveyardmall.com:
http://www.graveyardmall.com/categories/Daily-Deal/
has a Motorola Digital Video Baby Monitor with 2.4 LCD, NightVision and
two way communication for just $7499 + $6 shipping
Featuring infrared night vision for low-light surveillance, crystal-clear
sound for high-sensitivity eavesdropping and 2-way communication, so you can
also use it as an intercom. It even has an extended digital range of up to
450 feet and comes with a belt clip, so you can monitor from throughout your
... 阅读全帖 |
|
w*******y
发帖数: 60932 | 42 Genuine Windows 7 Home Premium 64-bit
AMD Dual-Core Processor E-350 (1.6GHz, 1MB L2 Cache)+AMD Radeon(TM) HD 6310M
Discrete-Class Graphics
FREE Upgrade to 3GB DDR3 System Memory (2 Dimm)
FREE Upgrade to 320GB 7200RPM Hard Drive with HP ProtectSmart Hard Drive
Protection
No Additional Office Software
No additional security software
6-Cell Lithium-Ion Battery (standard) - Up to 9.5 hours of battery life +++
11.6" diagonal High Definition HP BrightView LED Display (1366 x 768)
Webcam with Integrate... 阅读全帖 |
|
w*******y
发帖数: 60932 | 43 My first Post
Go to Hp.com and customze the HP TouchSmart tm2t series. Get $300off coupon
code is nb4545...only works if customized the way i am showing below: Also
free upgrade to 500GB Hard Drive
Basic Specs:
Usage: Business
Optical drive: External
Type: Your world at your fingertips
Processors: Intel Other
Battery Life: Up to 6 hours of battery life (6 cell)+++
Memory card reader: 5-in-1 integrated Digital Media Reader
Accessible memory slots: ... 阅读全帖 |
|
w*******y
发帖数: 60932 | 44 Another weekend deal from Frys. The Compaq CQ56-201NR 15.6" Notebook
usually retails for $429 but a budget laptop for $288 is a pretty good deal.
The link to the computer - Link:
http://www.frys.com/product/6516403?site=sr:SEARCH:MAIN_RSLT_PG
Please remember, B&M!
The specs -
Compaq Presario CQ56-201NR (XY872UA#ABA) Notebook PC
Mobility that matches your budget.
Enjoy the freedom of notebook computing at a great value. The Compaq
Presario CQ56 notebook PC features the latest technology and e... 阅读全帖 |
|
w*******y
发帖数: 60932 | 45 Seems like a good deal for a decent, basic, dual-core laptop w/ HDMI and N
wi-fi.
Link:
http://www.frys.com/product/6552603
Compaq CQ62-418NR 15.6" Notebook
HP:
FRYS.com #: 6552603
Detailed Description
(Manufacturer # CQ62-418NR )
Compaq Presario
CQ62-418NR Notebook PC (XZ276UA#ABA)
Function-forward.
The Presario CQ62 notebook comes preloaded with applications to enhance
your productivity and one-to... 阅读全帖 |
|
w*******y
发帖数: 60932 | 46 I didn't see this posted, so thought I would share. HP currently has $450
off the dv7t laptop. Depending upon your build, this can be better or worse
than 30% off.
1. Click here:
http://www.shopping.hp.com/series/category/notebooks/dv7tqe_ser
to start HP Home direct store, select Customize & Buy under Base
Configuration
2. Select FREE Upgrade to 6GB DDR3 System Memory (2 Dimm) +$0
3. Select FREE Upgrade to 750GB 5400RPM Hard Drive with HP ProtectSmart Hard
Drive Protection +$0
4. Select Free ... 阅读全帖 |
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w*******y
发帖数: 60932 | 47 Buy.com has the Acer H7530D DLP Projector - Refurbished for $499.95 with
free shipping.
Link:
http://www.buy.com/prod/acer-h7530d-dlp-projector-1080p-16-9-hd
The chic white Acer H7530D projector gives you Full HD 1080p widescreen
cinematic enjoyment with images in living colors! Complete HDMI connectivity
, ultra-high dynamic contrast ratio, and enhanced color technologies bring
you brilliant games and entertainment right in the comfort of your living
room.
Features
Tech Features USB Yes... 阅读全帖 |
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w*******y
发帖数: 60932 | 48 Coupon Code IWT44818
$899 for a 60" LCD
Enjoy watching movies, TV programs, or playing games in high-definition
through the Westinghouse VR-6025Z 60" Class LCD HDTV!
The Westinghouse VR-6025Z 60" Class LCD HDTV features its 59.9-inch diagonal
display with a display components of 1920 x 1080 native resolution, 5000:1
contrast ratio and 16:9 aspect ratio, assuring you of crisp images with
vibrant colors every time you watch your favorite TV shows, movies or
playing an intense game. It also boasts ... 阅读全帖 |
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