using System;

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = int.Parse(line[0]);
        var b = int.Parse(line[1]);
        var ans = (double)(b - a) * (b - a) * (b - a) / 6;
        Console.WriteLine(ans);
    }
}