import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int b1 = scan.nextInt();
		int b2 = scan.nextInt();
		int b3 = scan.nextInt();
		scan.close();
		int n = b2 * b2 + b3 * b3 - b1 * b3 - b2 * b3;
		int d = b2 - b1;
		int b4 = n / d;
		System.out.println(b4);
	}
}