func_code_string: #include <bits/stdc++.h>   using namespace std;   const int INF = 1e9 + 23;   const int MOD = 1e9 + 7;   const int N = 1000 + 10;   int brow[N], bcol[N];   int main() {     ios_base::sync_with_stdio(0);     int n, m;     cin >> n >> m;     for (int i = 0; i < (m); ++i) {       int x, y;       cin >> x >> y;       brow[x] = true;       bcol[y] = true;     }     int ans = 0;     for (int i = (2); i < (n); ++i) {       if (i == n - i + 1)         ans += !brow[i] || !bcol[i];       else {         ans += !brow[i];         ans += !bcol[i];       }     }     cout << ans <<   n ;     return 0;   }   