using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Runtime.Intrinsics.X86;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static string[] SList(long n) => Enumerable.Repeat(0, (int)n).Select(_ => ReadLine()).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (a, b) = (c[0], c[1]);
        var ans = 0.0;
        var d = 0.00001;
        for (var i = (double)a; i <= b; i += d)
        {
            ans += - (i - a) * (i - b) * d;
        }
        WriteLine(ans);
    }
}