package test;

import java.util.Scanner;

public class Main {
    public static void main(String[] args){
       Scanner in = new Scanner(System.in);
       int b1 = in.nextInt();
       int b2 = in.nextInt();
       int b3 = in.nextInt();
       System.out.println((int)(b3 * (b3 - b2) / ((b2 - b1) * 1.0) + b3 - b2 * (b3 - b2) / ((b2 - b1) * 1.0)));
    }
}