TrailingZeroInN

using System;

    class TrailingZeroInN
    {
        static void Main()
        {
            int n = int.Parse(Console.ReadLine());
            int zeroCounter = 0;
            int divider = 5;
            while (n / divider >= 1)
            {
                zeroCounter += n / divider;
                divider *= 5;
            }
            Console.WriteLine(zeroCounter);
        }
    }