func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long n, isum = 0;     cin >> n;     if (n % 2 == 0)       cout << ((n + 1) * (n + 1) - 1) / 4;     else       cout << ((n + 1) * (n + 1)) / 4;   }   