import math

def sieve_of_eratosthenes(n):
    prime = [True for i in range(n+1)]
    prime[0] = False
    prime[1] = False

    sqrt_n = math.ceil(math.sqrt(n))
    for i in range(2, sqrt_n):
        if prime[i]:
            for j in range(2*i, n+1, i):
                prime[j] = False

    return prime

n,p = map(int,input().split())
prm = sieve_of_eratosthenes(n)
pm = []
for i in range(n+1):
    if prm[i] == True:
        pm.append(i)

mr = set()

for i in range(len(pm)):
    if pm[i]*2 > n:
        #idx = i
        mr.add(pm[i])

#print(idx,pm[idx],len(pm)-idx)
if p in mr:
    print(1)
else:
    print(n-len(mr)-1)