import java.util.*;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		double a1 = sc.nextDouble();
		int a2 = sc.nextInt();
		int a3 = sc.nextInt();
		double r =(a3-a2)/(a2-a1);
		double d = a2-r*a1;
		System.out.println((int)(a3*r+d));
	}
}