[골3] 10986 - 나머지 합 구하기

#pragma region 입출력 속도향상

#define FAST_IO() \
{\
	ios::sync_with_stdio(false);\
	cin.tie(NULL); \
	cout.tie(NULL); \
}\

#pragma endregion

#include <iostream>
#include <vector>

using namespace std;

int main()
{
	FAST_IO();
	int n, m;
	cin >> n >> m;

	vector<long> v(n + 1), c(m);
	vector<long> s(n + 1);
	long ans = 0;

	for (int i = 1; i <= n; i++)
	{
		int tmp;
		cin >> tmp;
		v[i] = (v[i - 1] + tmp) % m;
		ans += (v[i] == 0);
		c[v[i]]++;
	}

	for (const auto& val : c)
		ans += (val * (val - 1) / 2);

	cout << ans;
	return 0;
}