为啥RE呀 有调必关

#include <bits/stdc++.h>
using namespace std;
const int N = 1e3 + 10;
int n,m,c;
long long a[N][N],ans[N][N];
int main()
{
	cin >> n >> m >> c;
	for(long long i = 1;i <= n;i++)
	{
		for(long long j = 1;j <= m;j++)
		{
			cin >> a[i][j];
			ans[i][j] = ans[i - 1][j] + ans[i][j - 1] - ans[i - 1][j - 1] + a[i][j];
		}
	}
	long long maxn = -INT_MAX;
	long long zuobiao1 = 0;
	long long zuobiao2 = 0;
	for(long long x1 = 1;x1 <= n - c + 1;x1++)
	{
		for(long long y1 = 1;y1 <= m - c + 1;y1++)
		{
			//x2 = x1 + c - 1
			//y2 = y1 + c - 1
			long long num = ans[x1 + c - 1][y1 + c - 1] - (ans[x1 + 1 - c][y1 + c - 1] + ans[x1 + c - 1][y1 + 1 - c] - a[x1 + 1 - c][y1 + 1 - c]);
			if(num > maxn)
			{
				maxn = num;
				zuobiao1 = x1;
				zuobiao2 = y1;
			}
		}
	}
	cout << zuobiao1 << " " << zuobiao2;
	return 0;
}