func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long n, m, a, b;     cin >> n >> m >> a >> b;     long long cost = 0;     if (m > n) m = n;     if (m * a <= b)       cost = n * a;     else {       cost = (n / m) * b;       n = n % m;       if (n > 0) {         if ((n)*a <= b)           cost += n * a;         else           cost += b;       }     }     cout << cost;     return 0;   }   