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()
    if l == 1:
        print(0)
        return
    m = r + 10
    s = [-1]*m
    for i in range(4, m, 2):
        s[i] = 2
    for i in range(3, m, 2):
        if s[i] < 0:
            for j in range(i*i, m, i):
                if s[j] < 0:
                    s[j] = i
    ans = 0
    for i in range(r, l, -1):
        if s[i] < l and i//s[i] < l:
            ans += 1
    print(ans)
    return

solve()