import java.util.Scanner;

public class No538 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long b1 = sc.nextLong();
		long b2 = sc.nextLong();
		long b3 = sc.nextLong();
		
		System.out.println((b3-b2)*(b3-b1)/(b2-b1)+b2);
	}
}