func_code_string: #include <bits/stdc++.h>   int main() {     int n, m;     int sum = 0;     int a, b;     int i = 0;     int x[1010] = {0}, y[1010] = {0};     scanf( %d %d , &n, &m);     while (m-- > 0) {       scanf( %d %d , &a, &b);       y[a] = 1;       x[b] = 1;     }     for (i = 2; i <= n - 1; i++) {       if (x[i] == 0) sum++;       if (y[i] == 0) sum++;     }     if (n % 2 == 1 && x[n / 2 + 1] == 0 && y[n / 2 + 1] == 0) sum--;     printf( %d n , sum);     return 0;   }   