func_code_string: #include <bits/stdc++.h>   using namespace std;   const bool ready = []() {     ios_base::sync_with_stdio(false);     cin.tie(0);     cout << fixed << setprecision(12);     return true;   }();   const double PI = acos(-1);   using ll = long long;   using pii = pair<ll, ll>;   using pdd = pair<double, double>;   using vd = vector<double>;   using vb = vector<bool>;   using vi = vector<ll>;   using vvi = vector<vi>;   using vs = vector<string>;   void solve() {     ll n;     cin >> n;     ;     ll m;     cin >> m;     ;     vb sx(n + 1);     vb sy(n + 1);     for (ll i = 0; i < m; i++) {       ll x;       cin >> x;       ;       ll y;       cin >> y;       ;       sx[x] = true;       sy[y] = true;     }     ll ans = 0;     for (ll i = 2; i < n / 2 + 1; i++) {       if (!sy[n - i + 1]) ans++;       if (!sy[i]) ans++;       if (!sx[n - i + 1]) ans++;       if (!sx[i]) ans++;     }     if (n & 1) {       if ((!sx[n / 2 + 1]) || (!sy[n / 2 + 1])) ans++;     }     cout << ans << endl;   }   signed main() { solve(); }   