func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, first, last, ans, flag;     cin >> n;     if (n <= 2) {       cout << 0 << endl;       return 0;     }     ans = flag = 0;     first = 1;     last = n;     for (int i = 1; i < n; i++) {       ans += (first + last) % (n + 1);       if (!flag) {         first++;         swap((first), last);       } else {         first--;         swap((first), last);       }       flag = 1 - flag;     }     cout << ans << endl;     return 0;   }   