import java.util.Scanner;

public class Exec0538 {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		long b1 = scan.nextInt();
		long b2 = scan.nextInt();
		long b3 = scan.nextInt();
		scan.close();
		long n = b2 * b2 + b3 * b3 - b1 * b3 - b2 * b3;
		long d = b2 - b1;
		long b4 = n / d;
		System.out.println(b4);
	}
}