import sys

N,P=map(int,input().split())

if P==1:
    print(1)
    sys.exit()

import math 
L=math.ceil(math.sqrt(P))

if P>N//2:
    for i in range(2,L+1):
        if P%i==0:
            break

    else:
        print(1)
        sys.exit()



L=math.floor(math.sqrt(N))#平方根を求める

Primelist=[i for i in range(N+1)]
Primelist[1]=0#1は素数でないので0にする.
 
for i in Primelist:
    if i>L:
        break
    if i==0:
        continue
    for j in range(2*i,N+1,i):
        Primelist[j]=0

Primes=[Primelist[j] for j in range(N+1) if Primelist[j]!=0]

import bisect
ANS=bisect.bisect_right(Primes,N//2)
print(N-(len(Primes)-ANS+1))