func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, g[20][20], r, c, k, ans = 0, x, y;   bool chk(int a, int b, int c, int d) {     int cnt = 0;     for (int i = a; i <= a + c; i++) {       for (int j = b; j <= b + d; j++) {         cnt += g[i][j];         if (cnt >= k) return 1;       }     }     return 0;   }   int main() {     scanf( %d%d%d%d , &r, &c, &n, &k);     for (int i = 0; i < n; i++) {       scanf( %d%d , &x, &y);       g[x][y] = 1;     }     for (int i = 1; i <= r; i++) {       for (int j = 1; j <= c; j++) {         for (int e = 0; e + i <= r; e++) {           for (int f = 0; f + j <= c; f++) {             ans += chk(i, j, e, f);           }         }       }     }     cout << ans;     return 0;   }   