l,r = map(int,input().split())
if l == 1:
    print(0)
    exit()
def judge(n):
    st = set()
    for i in range(1,int((n+0.5)**0.5+1)):
        if n%i == 0:
            if l <= i <= r or l <= n//i <= r:
                return 0
    return 1
ans = 0
for i in range(l,r+1):
    ans += judge(i)
print(ans)