using System;
using System.Linq;

public class P1009 {
    public static void Main() {
        var ab = Console.ReadLine().Trim().Split(' ').Select(int.Parse).ToList();
        var a = ab[0];
        var b = ab[1];
        var result = (b*b*b - a*a*a) / 3.0 - ((a + b) * (b*b - a*a)) / 2.0 + a*b*(b-a);
        Console.WriteLine(Math.Abs(result));
    }
}