# coding: UTF-8
import sys
#sys.setrecursionlimit(n)
import heapq
import re
import bisect
import random
import math
import itertools
from collections import defaultdict, deque
from copy import deepcopy
from decimal import *

def is_prime(n):
    i = 2
    while i * i <= n:
        if n % i == 0:
            return False
        i += 1
    return True
def prime_table(n):
    list = [True for _ in range(n + 1)]
    i = 2
    while i * i <= n:
        if list[i]:
            j = i + i
        while j <= n:
            list[j] = False
            j += i
        i += 1
    table = []
    for i in range(n + 1):
        if list[i] and i >= 2:
            table.append(1)
        else:
            table.append(0)
    return table


n, p = map(int, input().split())
table = prime_table(n)
if is_prime(p):
    print(1)
else:
    print(n - sum(table[0:n]) + 1)