#include <iostream>
#include <cassert>
typedef long long ll;
using namespace std;
template <class T> void setmin(T & a, T const & b) { if (b < a) a = b; }
const ll inf = ll(1e18)+9;
int main() {
    ll a, b, t; cin >> a >> b >> t;
    assert (a < b);
    ll ans = inf;
    for (int i = 0; i <= t; i += b) {
        setmin(ans, i + (t - i + a-1)/a*a);
    }
    cout << ans << endl;
    return 0;
}