using System;

public class Program

{

    public static void Main()

    {

        int n = 4; int x = 5;

        double sum = 0; double nr = 1; double dr = 1; double term =1;

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

        {

            sum = sum + term;

            nr = nr * x;

            dr = dr * i;

            term = nr / dr;

        }

        Console.WriteLine("Sum = " + sum);

    }

}