题目描述
Problem Statement
Let’s take a prime P = 200\,003.
You are given $N integers A_1, A_2, \ldots, A_N$.
Find the sum of $((A_i \cdot A_j) \bmod P)$ over all $N \cdot (N-1) / 2$ unordered pairs of elements (i < j).
Please note that the sum isn't computed modulo P.
Input
Input is given from Standard Input in the following format.
N
$A_1 A_2 \cdots A_N$
Output
Print one integer — the sum over $((A_i \cdot A_j) \bmod P)$.
Constraints
- $2 \leq N \leq 200$\,000
- $0 \leq A_i < P = 200$\,003
- All values in input are integers.
Sample Input 1
4
2019 0 2020 200002
Sample Output 1
474287
The non-zero products are:
- $2019 \cdot 2020 \bmod P = 78320$
- $2019 \cdot 200002 \bmod P = 197984$
- $2020 \cdot 200002 \bmod P = 197983$
So the answer is 0 + 78320 + 197984 + 0 + 0 + 197983 = 474287.
Sample Input 2
5
1 1 2 2 100000
Sample Output 2
600013
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分
样例输入
4
2019 0 2020 200002
样例输出
474287