using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Give me a number");

        int userInput = Convert.ToInt32(Console.ReadLine());

        int result = Factorial(userInput);

        Console.WriteLine(result);

    }

​

    public static int Factorial(int number)

    {

        if (number < 0)

        {

            Console.WriteLine("Number cannot be negative.");

        }

​

        int factorial = 1;

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

        {

            factorial *= i;

        }

​

        return factorial;

    }

}