using System;

public class Program

{

    public int status = 9;

    public static void Main()

    {

        int i =  9;

        var result = factor(i);

        Console.WriteLine( result.ToString());

    }

    public static int factor(int a)

    {

        var old = 1;

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

        //{

        //  old = n*old;

    //  }

        if (a!= 0)

            old = a*old;

            return  factor(a-1);

    }

}