using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Nhap n = ");

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

        int s = 0;

        int i = 1;

        while(i <= n)

        {

            int giaiThuaCuaI = 1;

            int j =1;

            while (j <= i)

            {

                giaiThuaCuaI = giaiThuaCuaI * j;

                j++;

            }

            s = s + giaiThuaCuaI;

            i++;

        }

        Console.WriteLine($"Result = {s}");

    }

}