#include "bits/stdc++.h"
using namespace std;


int main() {
	long long A, B, T;
	cin >> A >> B >> T;
	long long ans = (long long)1e10;
	for (int i = 0; i < 2000000 && A * (i - 1) < T; i++)
	{
		long long num = A * i;

		num += ((T - num) / B) * B;
		while (num < T) num += B;
		ans = min(num, ans);
	}
	cout << ans << endl;
}