Score : 600 points
Given are a sequence of N integers A_1, A_2, \ldots, A_N and a positive integer S.
For a pair of integers (L, R) such that 1\leq L \leq R \leq N, let us define f(L, R) as follows:
Find the sum of f(L, R) over all pairs of integers (L, R) such that 1\leq L \leq R\leq N. Since this sum can be enormous, print it modulo 998244353.
Input is given from Standard Input in the following format:
N S A_1 A_2 ... A_N
Print the sum of f(L, R), modulo 998244353.
3 4 2 2 4
5
The value of f(L, R) for each pair is as follows, for a total of 5.
5 8 9 9 9 9 9
0
10 10 3 1 4 1 5 9 2 6 5 3
152