import java.util.Scanner;

public class Main{
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		while(sc.hasNext()){
			long a=sc.nextLong();
			long b=sc.nextLong();
			if(a==b) System.out.println(0);
			else System.out.println((a*a-b*b)/(a-b));
		}
	}
}