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