DMOPC '17 Contest 1 P2 - Sharing Crayons
View as PDFMimi is helping out at a daycare! There are  children and 
 boxes of crayons in a row, the 
 of which has 
 crayons. Mimi will choose a single contiguous section of crayon boxes to give to the children. In order to be fair, she also wants the total number of crayons in the subarray she chooses to be divisible by 
 so that it can be split equally. How many ways can she do this?
Constraints
For all subtasks:
Subtask 1 [20%]
Subtask 2 [20%]
Subtask 3 [40%]
Subtask 4 [20%]
Input Specification
The first line will have two space separated integers,  and 
.
The second line will have  space separated integers, 
.
Output Specification
A single integer, the number of subarrays which have a total which is a multiple of . This number may overflow 32-bit integers.
Sample Input
5 6
3 5 9 6 10
Sample Output
2
Explanation for Sample
The two subarrays with a sum divisible by 6 are  and 
.
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