SUMSUMS - Summing Sums

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The N (1 ≤ N ≤ 50,000) cows, conveniently numbered 1, 2, ..., N, are trying to learn some encryption algorithms. After studying a few examples, they have decided to make one of their own! However, they are not very experienced at this, so their algorithm is very simple:

Each cow i is given a starting number Ci (0 ≤ Ci < 90,000,000), and then all the cows perform the following process in parallel:

  • First, each cow finds the sum of the numbers of the other N-1 cows.
  • After all cows are finished, each cow replaces her number with the sum she computed. To avoid very large numbers, the cows will keep track of their numbers modulo 98,765,431.

They told Canmuu the moose about it in November; he was quite impressed. Then one foggy Christmas Eve, Canmuu came to say:

"Your algorithm is too easy to break! You should repeat it T (1 ≤ T ≤ 1,414,213,562) times instead."

Obviously, the cows were very frustrated with having to perform so many repetitions of the same boring algorithm, so after many hours of arguing, Canmuu and the cows reached a compromise: You are to calculate the numbers after the encryption is performed!


  • Line 1: Two space-separated integers: N and T.
  • Lines 2..N+1: Line i+1 contains a single integer: Ci.


  • Lines 1..N: Line i contains a single integer representing the number of cow i (modulo 98,765,431) at the end of the encryption.


3 4


The following is a table of the cows' numbers for each turn:

          Cows' numbers
Turn    Cow1  Cow2  Cow3
 0        1     0     4
 1        4     5     1
 2        6     5     9
 3       14    15    11
 4       26    25    29
Warning: large input/output data.

hide comments
infyy: 2018-06-01 10:15:44

Getting WA in last test case even though I have used 98765431

druh: 2017-12-01 14:24:58

WA on 14 :( Help PLEASE!

fresh: 2016-01-27 04:14:24

sorry for that
getting wrong answer you may probably derived the recurrence for some fixed n and that's wrong, the recurrence is related to n. also consider the case n = 1

fresh: 2016-01-26 14:49:21

there is something wrong with this problem
int main()
the above code gets TLE on test 14 ! and it pass the previous ones

=(Francky)=> You have TLE for each test, and TLE is shown for the last one. Please do not post code here next time !

Last edit: 2016-01-26 16:29:49
Mahmoud A Gawad: 2015-10-11 18:27:30

1. Don't use scanf("%I64d",...) -> It will give you WA in test 14
2. Take care of (x*y*z)%mod -> (( (x*y)%mod)* z)%mod
and (x+y+z)%mod as well.

Harish Meena: 2015-10-01 17:55:18

why is number 14 giving WA??

:|: 2015-01-23 08:52:19

@kriti, how ans can be <0. all things are summation of positive integers only!

Kriti Joshi: 2014-12-19 05:39:53

@Doshi I think it is O(n+log(t)). WA at test case 8 may be due to not including if(ans<0)ans+=98765431

Last edit: 2014-12-19 06:20:32
gyosh: 2014-10-17 07:46:07

If you are getting WA in test case 14, you probably typed 987654321 as the modulo. The correct number is 98765431 (without 2)

Pratyush Kar: 2014-07-19 19:50:01

nice question

Added by:Neal Wu
Time limit:0.160s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ERL JS-RHINO
Resource:USACO Chn 2007