#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;

	rep(j, A) {
		long long i = (T-B*j+A-1)/A;
		if(A*i+B*j >= T) {
			std::cout << A*i+B*j << "\n";
			break;
		}
	}

	return 0;
}