Programming Fundamentals - 14. Factorial Trailing Zeroes

using System;
using System.Numerics;

namespace _04b_MethodsDebuggingTroubleshootingCode_Exercises
{
    class MethodsDebuggingTroubleshootingCode_Exercises
    {static void Main(string[] args)
        {
            BigInteger num = BigInteger.Parse(Console.ReadLine());

            Console.WriteLine($"{CalculateTrailingZeroes(Factorial(num))}");
        }

        static BigInteger Factorial(BigInteger num)
        {
            if (num <= 1)
                return 1;
            return num * Factorial(num - 1);
        }

        static int CalculateTrailingZeroes(BigInteger num)
        {
            int zeroesCounter = 0;

            while (num % 10 == 0)
            {
                zeroesCounter++;
                num /= 10;
            }

            return zeroesCounter;
        }
    }
}