import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double b1 = sc.nextInt();
        double b2 = sc.nextInt();
        double b3 = sc.nextInt();
        double r = (b2 - b3) / (b1 - b2);
        double d = b2 - b1 * r;
        double ans = r * b3 + d;
        System.out.println((long)(Math.round(ans)));
    }
}