func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 15;   const int K = 500;   int a[N][N];   const int INF = 1e9 + 7;   int calc(int x, int y, int h, int w) {     int cnt = 0;     for (int i = x; i < x + h; i++) {       for (int j = y; j < y + w; j++) {         cnt += a[i][j];       }     }     return cnt;   }   int main() {     int r, c;     int n, k;     cin >> r >> c >> n >> k;     for (int i = 0; i < n; i++) {       int x, y;       cin >> x >> y;       x--;       y--;       a[x][y] = 1;     }     int ans = 0;     for (int d = 1; d <= r; d++) {       for (int w = 1; w <= c; w++) {         for (int i = 0; i + d - 1 < r; i++) {           for (int j = 0; j + w - 1 < c; j++) {             if (calc(i, j, d, w) >= k) ans++;           }         }       }     }     cout << ans;   }   