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