#include <iostream>
#include <map>
#include <cmath>
#define int long long
#define EPS 1e-9
#define INF 1e+9
using namespace std;

signed main() {
	double a,b,c,r,d;
	cin >> a >> b >> c;
	r = (c - b) / (b - a);
	d = b - a * r;
	cout << (int)(r * c + d + (r * c + d) * EPS / INF) << endl;
	return 0;
}