DevidibleBy5

using System;

class NumsInIntervalDividableByFive
{
    static void Main(string[] args)
    {
        int start = int.Parse(Console.ReadLine());
        int end = int.Parse(Console.ReadLine());
        int p = 0;

        while ( start % 5 != 0 ) {
            ++start;
            if (start == end && start % 5 != 0) {
                Console.WriteLine(p);
                Environment.Exit(0);
            }
        }

        p = ((end - start) / 5) + 1;
        Console.WriteLine(p);
    }
}