using System;

namespace Example63
{
	/// <summary>
	/// Summary description for Class1.
	/// </summary>
	class Class1
	{
		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]
		static void Main(string[] args)
		{
			Console.Write("Input n: ");
			int n = int.Parse(Console.ReadLine());
			Console.WriteLine("{0}! = {1}", n, fact(n));
		}

		static int fact(int n)
		{
			if (n == 0)
				return 1;
			else
				return n * fact(n - 1);
		}
	}
}