#Thanks for https://judge.yosupo.jp/submission/33263
from math import sqrt
def prime_counting(n):
    if n<=1:
        return 0

    n2 = int(n ** 0.5)
    ndn2 = int(n / n2)
    hl = [0] * ndn2
    for i in range(1, ndn2):
        hl[i] = int(n / i) - 1
    hs = list(range(-1, n2))
    pi = 0
    for x in range(2, n2 + 1):
        if hs[x] == hs[x - 1]:
            continue
        x2 = x * x
        imax = min(ndn2, int(n / x2) + 1)
        ix = x
        for i in range(1, imax):
            if ix < ndn2:
                hl[i] -= hl[ix]
            else:
                hl[i] -= hs[int(n / ix)]
            hl[i] += pi
            ix += x
        for k in range(n2, x2 - 1, -1):
            hs[k] -= hs[int(k / x)] - pi
        pi += 1
    return hl[1]
#==================================================
L,R=map(int,input().split())

alpha=prime_counting(R)-prime_counting(L-1)
beta =prime_counting(2*R)-prime_counting(2*L)

print(alpha+beta)