func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, m;     cin >> n >> m;     vector<bool> x;     vector<bool> y;     x.assign(n + 1, 1);     y.assign(n + 1, 1);     x[1] = 0;     y[1] = 0;     x[n] = 0;     y[n] = 0;     for (int i = 0; i < m; i++) {       int tmp_x, tmp_y;       scanf( %i %i , &tmp_x, &tmp_y);       x[tmp_x] = 0;       y[tmp_y] = 0;     }     int result = 0;     for (int i = 1; i <= n / 2; i++) {       if (i * 2 != n + 1) {         if (x[i] == 1) result++;         if (x[n - i + 1] == 1) result++;         if (y[i] == 1) result++;         if (y[n - i + 1] == 1) result++;       }     }     if (n % 2 == 1)       if ((x[n / 2 + 1] == 1) || (y[n / 2 + 1] == 1)) result++;     cout << result << endl;     return 0;   }   