#include <iostream>
using namespace std;

int main(void){
    int b1, b2, b3;
    cin >> b1 >> b2 >> b3;
    
    double r, d;
    r = (b3-b2)/(double)(b2-b1);
    d = b2 - r * b1;
    
    cout << (int)(r * b3 + d) << endl;
}