using System;

public class Program
{
    static void Main()
    {
        string s = Console.ReadLine();
        string[] t = s.Split(' ');
        int a = int.Parse(t[0]);
        int b = int.Parse(t[1]);
        int dif = b - a + 1;
        int result = (dif / 3)|0 + ((((a + b) % 3 == 0)||((a + b)%3 + dif % 3)>=3) ? 1 : 0);
        Console.WriteLine(result);
    }
}