using System;

​

public static class NewMathExtensions {

    public static double Factorial(this int n) {

        double multi = 1;

        for(int i=n; i>1; i--) {

            multi *= i;

        }

        return multi;

    }

}

public static class Lattice {

    public static double FindLatticePathCount(int n) {

        double count = (2 * n).Factorial()/Math.Pow((3).Factorial(), 2);

        return count;

    }

}

public class Program

{

    public static void Main()

    {

        //Console.WriteLine(Lattice.FindLatticePathCount(2));

    }

}