﻿using System;
/*Problem 11.* Numbers in Interval Dividable by Given Number
------------------------------------------------------------------------------------------------------------------------
Write a program that reads two positive integer numbers and prints how many numbers p exist between them such that the reminder of the division by 5 is 0.
Examples:

start	end		p		comments
17		25		2		20, 25
5		30		6		5, 10, 15, 20, 25, 30
3		33		6		5, 10, 15, 20, 25, 30
3		4		0		-
99		120		5		100, 105, 110, 115, 120
107		196		18		110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195
*/

class NumbersInInterval
{
	static void Main()
	{
		int start = int.Parse(Console.ReadLine());
		int end = int.Parse(Console.ReadLine());
		int p = 0;

		for (int i = start; i <= end; i++)
		{
			if (i % 5 == 0) p++;
		}
		Console.WriteLine(p);
	}
}