#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const ll INF = 2e9;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	ll a, b, t;
	cin >> a >> b >> t;
	ll ans = INF;
	for (ll i = 0; i < a; i++) {
		if (t < b * i) {
			ans = min(ans, b * i);
			break;
		}
		ll cnt = (t - b * i + a - 1) / a;
		ans = min(ans, cnt * a + b * i);
	}
	cout << ans << endl;
	return 0;
}