#include <iostream>
using namespace std;
template <class T> void setmin(T & a, T const & b) { if (b < a) a = b; }
const int inf = 1e9+7;
int main() {
    int a, b, t; cin >> a >> b >> t;
    int ans = inf;
    for (int i = 0; i <= t; i += b) {
        setmin(ans, i + (t - i + a-1)/a*a);
    }
    cout << ans << endl;
    return 0;
}