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

int main(void) {
	ll a,b,t;
	cin >> a >> b >> t;
	ll ret = 1LL<<60;
	for(ll y=0;y*b <= t+b && y<=a;y++){
		ret = min(ret,y*b + (t -y*b + a-1)/a*a);
	}
	cout << ret << endl;
	return 0;
}