func_code_string: #include <bits/stdc++.h>   using namespace std;   int row[1008], col[1008], n, m, a, b, cnt;   int main() {     cin >> n >> m;     for (int i = 0; i < n + 1; i++) row[i] = col[i] = true;     while (m--) {       cin >> a >> b;       row[a] = col[b] = false;     }     for (int i = 2; i < n; i++) cnt += (row[i] + col[i]);     if (n % 2) cnt -= (row[n / 2 + 1] && col[n / 2 + 1]);     cout << cnt << endl;     return 0;   }   