using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

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

        int sum=0;

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

        {

            sum+=factorial(a);

            if(a<n)

            Console.Write("{0}!+",a);

        else

            Console.Write("{0}!= {1}",a,sum);

        }

    }

    public static int factorial(int n)

        {

            int a=n;

            int f=1;

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

            {

                f=f*x;

            }

            return f;

        }

}

​

​