Loops/Task 9/10 - Catalan numbers

using System;
using System.Numerics;
class CatalanNumbers
{
    static void Main()
    {
        int num = int.Parse(Console.ReadLine());
        BigInteger factTwoN=1, factN=1, factNOne=1;
        int doubleNum = 2*num;
        int numPlusOne = num+1;
        while (num > 0)
        {
            factN *= num;
            num--;
        }
        while (doubleNum > 0)
        {
            factTwoN *= doubleNum;
            doubleNum--;
        }
        while (numPlusOne > 0)
        {
            factNOne *= numPlusOne;
            numPlusOne--;
        }
        Console.WriteLine(factTwoN/(factNOne*factN));
    }
}