#include <iostream>
#include <vector>
#include <cmath>

using namespace std;

int main(void){
    double a, b, c;
    cin >> a >> b >> c;
    long long ans = round( (c*((c-b)/(b-a))+b) -(a*((c-b)/(b-a))));
    cout << ans << endl;
    return 0;
}