class Program
{
    static void Main(string[] args)
    {
        string[] input = Console.ReadLine()!.Split(' ');
        int min = int.Parse(input[0]);
        int max = int.Parse(input[1]);
        int count = 0;
        
        for (int i = min; i <= max; i++)
        {
            double ave = (min + max + i) / 3.0;
            if (!ave.ToString().Contains("."))
            {
                count++;
            }
        }
        Console.WriteLine(count);
    }
}