11437: ABC378 - E - Mod Sigma Problem
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Description
You are given a sequence $A = (A_1, A_2, \dots, A_N)$ of $N$ non-negative integers, and a positive integer $M$.
Find the following value:
$
\sum_{1 \leq l \leq r \leq N} \left( \left(\sum_{l \leq i \leq r} A_i\right) \mathbin{\mathrm{mod}} M \right).
$
Here, $X \mathbin{\mathrm{mod}} M$ denotes the remainder when the non-negative integer $X$ is divided by $M$.
Find the following value:
$
\sum_{1 \leq l \leq r \leq N} \left( \left(\sum_{l \leq i \leq r} A_i\right) \mathbin{\mathrm{mod}} M \right).
$
Here, $X \mathbin{\mathrm{mod}} M$ denotes the remainder when the non-negative integer $X$ is divided by $M$.
Input
The input is given from Standard Input in the following format:
```
$N$ $M$
$A_1$ $A_2$ $\dots$ $A_N$
```
```
$N$ $M$
$A_1$ $A_2$ $\dots$ $A_N$
```
Output
Print the answer.
Constraints
- $1 \leq N \leq 2 \times 10^5$
- $1 \leq M \leq 2 \times 10^5$
- $0 \leq A_i \leq 10^9$
- $1 \leq M \leq 2 \times 10^5$
- $0 \leq A_i \leq 10^9$
Sample 1 Input
3 4
2 5 0
Sample 1 Output
10
- $A_1 \mathbin{\mathrm{mod}} M = 2$
- $(A_1+A_2) \mathbin{\mathrm{mod}} M = 3$
- $(A_1+A_2+A_3) \mathbin{\mathrm{mod}} M = 3$
- $A_2 \mathbin{\mathrm{mod}} M = 1$
- $(A_2+A_3) \mathbin{\mathrm{mod}} M = 1$
- $A_3 \mathbin{\mathrm{mod}} M = 0$
The answer is the sum of these values, $10$. Note that the outer sum is not taken modulo $M$.
- $(A_1+A_2) \mathbin{\mathrm{mod}} M = 3$
- $(A_1+A_2+A_3) \mathbin{\mathrm{mod}} M = 3$
- $A_2 \mathbin{\mathrm{mod}} M = 1$
- $(A_2+A_3) \mathbin{\mathrm{mod}} M = 1$
- $A_3 \mathbin{\mathrm{mod}} M = 0$
The answer is the sum of these values, $10$. Note that the outer sum is not taken modulo $M$.
Sample 2 Input
10 100
320 578 244 604 145 839 156 857 556 400
Sample 2 Output
2736