import math

def sqrt(n):
	ins = math.floor(math.sqrt(n))
	if ins**2 > n:
		ins -= 1
	return ins

l,r = map(int,input().split())
w = [0 for i in range(r-l+1)]
		
dp = [0 for i in range(10**6+1)]
for i in range(2, 10**6):
	if dp[i] == 0:
		#A/(i**2) = integer
		for j in range((l+i**2-1)//(i**2), r//(i**2)+1):
			w[j*(i**2) - l] = 1
		#A/i = square
		for j in range(max(2,sqrt((l-1)//i)+1), sqrt(r//i)+1):
			#print(j**2 * i)
			w[i*(j**2) - l] = 1
		for j in range(i, 10**6+1, i):
			dp[j] = 1

for i in range(r-l+1):
	#print(sqrt(l+i))
	if l+i > 1 and sqrt(l+i) ** 2 == l+i:
		w[i] = 1

print(r-l+1 - sum(w))