import sys

readline = sys.stdin.readline

ns = lambda: readline().rstrip()
ni = lambda: int(readline().rstrip())
nm = lambda: map(int, readline().split())
nl = lambda: list(map(int, readline().split()))

def solve():
    l, r = nm()
    s = [1]*(r+1)
    for i in range(l, r+1):
        for j in range(i*2, r+1, i):
            s[j] = 0
    print(sum(s[l+1:]))
    return

solve()