import math

l,r = map(int,input().split())
v = [l+i for i in range(r-l+1)]
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:
		for j in range(r-l+1):
			if v[j]%(i**2) == 0:
				w[j] = 1
			while v[j]%i == 0:
				v[j]//=i
		for j in range(i, 10**6+1, i):
			dp[j] = 1

#残ったもの… 10**12 - 10**18

for j in range(r-l+1):
	if w[j] == 0:
		ins = math.floor(math.sqrt(v[j] // 2))
		if ins**2 > v[j]:
			ins -= 1
		if ins > 1 and ins**2 == v[j]:
			w[j] = 1

#print(w)

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