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

namespace ConsoleApplication1
{
    class Program
    {
        static double F_Rec(int n, int i, out double res)
        {
            if (n <= 0)
                return res = 0;
            if (i != n)
                return res = Math.Sqrt(i + F_Rec(n, i + 1, out res));
            else return  res = Math.Sqrt(n);

        }

        static void Main(string[] args)
        {
            int i = 1;
            double res;
            Console.Write("Введите N: ");
            int n = int.Parse(Console.ReadLine());
            Console.WriteLine(F_Rec(n, i, out res) == 0 ? "Функция не определена" : (n / F_Rec(n, i, out res)).ToString());
        }
    }
}