为什么 MLE

# include <cstdio>
# include <iostream>
# include <algorithm>
using namespace std;

int a[5002][5002], s[5002][5002];

int main()
{
	int n, m;
	cin >> n >> m;
	for (int i = 1; i <= n; i++)
	{
		int x, y, v;
		cin >> x >> y >> v;
		x++, y++;
		a[x][y] = v;
	}
	for (int i = 1; i <= 5001; i++)
		for (int j = 1; j <= 5001; j++)
			s[i][j] = s[i - 1][j] + s[i][j - 1] - s[i - 1][j - 1] + a[i][j];
	int maxv = -1;
	for (int i = 1; i <= 5001; i++)
		for (int j = 1; j <= 5001; j++)
		{
			int u = max(0, i - m), v = max(0, j - m);
			int vv = s[u][v] - s[i][v] - s[u][j] + s[i][j];
			if (vv > maxv) maxv = vv;
		}
	cout << maxv << endl;
	return 0;
}