using System;

public class Program

{

    public static double sumSqrt(int x, uint n)

    {

        double s = 0;

        for(uint i = 1; i <= n; i++)

        {

            s = Math.Sqrt( Math.Pow(x, i) + s);

        }

        return s;

    }

    public static void Main()

    {

        Console.WriteLine(sumSqrt(2, 3));

    }

}