using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var input = Console.ReadLine().Split().Select(double.Parse).ToArray();
        var N = input[0];
        var K = input[1];
        Console.WriteLine("{0:0.0}", N * (N + 1) / 2 / (N + 1));
    }
}