#include <bits/stdc++.h>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)

int main() {

	long long A, B, T; cin >> A >> B >> T;
	long long min = 1e10;
	rep(j, A) {
		long long i = (T-B*j+A-1)/A;
		min = std::min(min, A*i+B*j);
		if(i > A) { break; }
	}

	std::cout << min << "\n";

	return 0;
}