using System;

​

public class Program

{

    static double Sum1(int n)

    {

        if (n == 1)

        {

            return 1;

        }

        else

        {

            return Math.Sqrt(n + Sum1(n - 1));

        }

    }

​

    public static void Main()

    {

        Console.WriteLine("Vuvedi n: ");

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

        double res = Sum1(n);

        Console.WriteLine(res);

    }

}