using System;

public class Program

{

    public static void Main()

    {

        Console.Write("Enter an integer number greater than or equal to 0: ");

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

​

        if (number < 0)

        {

            Console.WriteLine("Please enter a non-negative integer.");

        }

        else

        {

            long factorial = CalculateFactorial(number);

            Console.Write($"{number}! = ");

            for (int i = number; i >= 1; i--)

            {

                Console.Write(i);

                if (i > 1)

                {

                    Console.Write(" x ");

                }

            }

            Console.WriteLine($" = {factorial}");

        }

    }

​

    private static long CalculateFactorial(int n)

    {

        if (n == 0)

        {

            return 1;

        }

​

        long result = 1;

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

        {

            result *= i;

        }

​

        return result;

    }

}