func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, m, a[555][555], e[555][555], s, ans = -1e9;   int sum(int x, int y, int xx, int yy) {     return e[xx + 1][yy + 1] - e[x][yy + 1] - e[xx + 1][y] + e[x][y];   }   int main() {     cin >> n >> m;     for (int i = 0; i < n; i++)       for (int j = 0; j < m; j++) scanf( %d , &a[i][j]);     for (int i = 0; i < n; i++)       for (int j = 0; j < m; j++)         e[i + 1][j + 1] = e[i][j + 1] + e[i + 1][j] - e[i][j] + a[i][j];     for (int i = 1; i < n - 1; i++)       for (int j = 1; j < m - 1; j++) {         s = sum(i - 1, j - 1, i + 1, j + 1) - a[i][j] - a[i][j - 1];         ans = max(ans, s);         for (int k = 2;; k++) {           if (i - k < 0 || j - k < 0 || i + k >= n || j + k >= m) break;           s = sum(i - k, j - k, i + k, j + k) - s - a[i - k + 1][j - k];           ans = max(ans, s);         }       }     cout << (ans) << endl;     return 0;   }   