using System.Collections.Generic;
using System.Linq;
using System;

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var n = int.Parse(line[0]);
        var p = int.Parse(line[1]);
        var n1 = GeneratePrime(n).Count();
        var n2 = GeneratePrime(n / 2).Count();
        var noPhone = n1 - n2 + 1;
        var Phone = n - n1 + n2 - 1;
        Console.WriteLine(IsPhoneG(n, p) ? Phone : 1);
    }
    static bool IsPhoneG(int n, int p)
    {
        if (p == 1) return false;
        if (!IsPrime(p)) return true;
        if (IsPrime(p) && p * 2 <= n) return true;
        return false;
    }
    static bool IsPrime(int n)
    {
        if (n < 2) return false;
        else if (n == 2) return true;
        else if (n % 2 == 0) return false;
        double sqrtNum = Math.Sqrt(n);
        for (int i = 3; i <= sqrtNum; i += 2)
            if (n % i == 0) return false;
        return true;
    }
    static List<int> GeneratePrime(int m)
    {
        var a = new List<int>();
        int p;
        var sqrtMax = Math.Sqrt(m);
        var s = Enumerable.Range(2, m - 1).ToList();
        do
        {
            p = s.First();
            a.Add(p);
            s.RemoveAll(n => n % p == 0);
        }
        while (p < sqrtMax);
        a.AddRange(s);
        return a;
    }

}