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((l+i**2-1)//(i**2), r//(i**2)+1):
			w[j*(i**2) - l] = 1
			#print(j*(i**2))
			#print(j*(i**2) - l)
		for j in range(i, 10**6+1, i):
			dp[j] = 1

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