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

memo = [-1]*(N+1)
for i in range(2, N+1):
    if memo[i] > -1:
        continue
    memo[i] = 1
    j = 2*i
    while j <= N:
        memo[j] = 0
        j += i

if P > 1:
    L = [0]*(N+1)
    n = 2
    num = P
    while n <= P**0.5:
        if P%n == 0:
            num = n
            break
        n += 1
    if num*2 <= N:
        ans = N//2-1
        for i in range(N//2+1, N+1):
            if memo[i] == 0:
                ans += 1
    else:
        ans = 1

print(ans)