public class Program

{

    public static int fact(int num) 

    {

        int mahpela=num, sifra=num;

        while (sifra>1)

        {

            sifra=sifra-1;

            mahpela=mahpela* sifra;

        }

        return mahpela;

    }

    public static void Main()

    {

        int mainnum, factorial;

        Console.WriteLine("write a number");

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

        if(mainnum>1)

            factorial=fact(mainnum);

        else

            factorial= mainnum;

        Console.WriteLine(mainnum+" factorial is "+factorial);

    }

}