FactorialTrailingZeros

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        int number = int.Parse(Console.ReadLine());
        int totalZeroes = 0;

        for (int i = 1; i < number ; i++)
        {
            totalZeroes += number / (int)Math.Pow(5, i);

            if ((number / Math.Pow(5, i)) == 0)
            {
                break;
            }
        }

        Console.WriteLine(totalZeroes);
    }
}