//ML2

import java.util.*;
import java.lang.*;
import java.io.*;

class First
{
	public static void main (String[] args) throws java.lang.Exception
	{
		double x, y, solution;
		Scanner input = new Scanner(System.in);
		
		x = input.nextDouble();
		y = input.nextDouble();
		
		solution = (Math.abs(x) - Math.abs(y)) / (Math.abs(x) + Math.abs(y));
		
		System.out.println(solution);
	}
}