#include <bits/stdc++.h>

using namespace std;

int A,B,T;
int main(){
  cin >> A >> B >> T;
  long long res = 1LL << 50;
  for (int i = 0;; i++){
    int j = (T - B * i + A - 1) / A;
    long long next = B * i +  A *j;
    res = min(res, next);
    if (B * i > T || i > A){
      break;
    }
  }
  cout << res << endl;
  return 0;
}