func_code_string: #include <bits/stdc++.h>   using namespace std;   bool row[1100], col[1100];   int main() {     int n, m;     while (scanf( %d %d , &n, &m) != EOF) {       memset(row, true, sizeof(row));       memset(col, true, sizeof(col));       while (m--) {         int x, y;         scanf( %d %d , &x, &y);         row[x] = false;         col[y] = false;       }       int res = 0;       for (int i = 2; i <= n - 1; i++) {         if (n % 2 && i == n / 2 + 1) {           continue;         }         if (col[i]) {           res++;         }         if (row[i]) {           res++;         }       }       if (n % 2 && (col[n / 2 + 1] || row[n / 2 + 1])) {         res++;       }       printf( %d n , res);     }     return 0;   }   