using System;

public class Program

{

    public static void Main()

    {

    int i, n, mauso,x;

    long tich;

    float tong;

    Console.Write("Nhap n: ");

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

    Console.Write("Nhap x: ");

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

    i = 1;

    tong = 0;

    tich = 1;

    mauso = 0;

        while (i<=n)

        {

            mauso = mauso + i;

            tich = tich*x;

            tong += 1.0f*tich/mauso;

            i++;

        }   

​

    Console.Write("Tong la: {0}",tong);

    }

}