using System;

public class Program

{

    public static void Main()

    {

            int input = int.Parse(Console.ReadLine());

            var sum = 0;

            for (var i = 1; i <= input; i++)

            {

                sum = sum + i;

            }

            double result = Convert.ToDouble(sum) / Convert.ToDouble(input);

​

            Console.WriteLine(result);

            Console.ReadLine();

    }

}