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Mr Makor And His Friends

By ovis96 · Limits 2s, 512 MB

Mr Makor has a set S of n integers. He calls a sequence of length k special if every element of the sequence is taken from the set S (the sequence can have the same element multiple numbers of times) and the summation of every two consecutive elements is divisible by m. More formally, if A is a sequence of length k and Ai is the ith element of the sequence then sequence A will be special if Ai ϵ S for every 1 ≤ i ≤ k and m | (Ai + Ai+1) (means m divides Ai + Ai+1) for every 1 ≤ i < k. Mr Makor was thinking about giving some sequences to his friends as a gift. So he thought about the number of distinct special sequences he can make. As this number may be quite large, you need to find its remainder modulo (109+7).

Note: Two sequences will be different if there exists an index where two sequences have two different values at that index.


The first line will contain an integer n(1 ≤ n ≤ 106). Next line will contain n distinct integers Si(1 ≤ Si ≤ 109) where Si is the ith element of the set.

The last line will contain two integers k and m (1 ≤ k, m ≤ 109).


Output the number of unique special sequences Mr Makor can make modulo (109+7).


6 4
2 10



94% Solution Ratio

mohanr7073Earliest, 5M ago

kzvd4729Fastest, 0.7s

EgorKulikovLightest, 55 MB

kzvd4729Shortest, 672B


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