func_code_string: #include <bits/stdc++.h>   using namespace std;   bool r[1010], c[1010];   int main() {     int n, m;     cin >> n >> m;     for (int i = 0; i < m; i++) {       int a, b;       cin >> a >> b;       a--;       b--;       r[a] = 1;       c[b] = 1;     }     int ans = 0;     for (int i = 1; i < n - 1; i++) {       if (!c[i]) ans++;       if (!r[i]) ans++;       if (!c[i] && !r[i] && !c[n - i] && !r[n - i] && (n - 1 - i) == i) ans--;     }     cout << ans << endl;   }   