#include <algorithm>
#include <vector>
#include <cfloat>
#include <string>
#include <cmath>
#include <set>
#include <cstdlib>
#include <map>
#include <ctime>
#include <iomanip>
#include <functional>
#include <deque>
#include <iostream>
#include <cstring>
#include <queue>
#include <cstdio>
#include <stack>
#include <climits>
#include <sys/time.h>
#include <cctype>

using namespace std;

typedef long long ll;

int main() {
  ll a, b, t;
  cin >> a >> b >> t;
  ll minv = a*(t/a+1);
  for (ll i = 0; i <= a && i*b <= t+b; i++) {
    minv = min(b*i+a*((t-b*i+a-1)/a), minv);
  }
  std::cout << minv << std::endl;
}