#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main() {
    ll A, B, T;
    cin >> A >> B >> T;

    ll ans = 2e9;
    for (int i = 0; i < A && i * B < T + B; i++) {
        ans = min(ans, i * B + ((T - i * B + A - 1) / A) * A);
    }

    cout << ans << endl;
}