using System;

public class Program

{

         public static int Fact(int x)

        {

            int m = 1;

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

                m = m * i;

​

            return m;

        }

        public static int Fact1(int d)

        {

            int sum = 0;

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

             sum = sum + Fact(i);

            return sum;

        }

        public static void Main(string[] args)

        {

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

           Fact(v);

            Console.WriteLine(Fact1(v));

        }

    }

​