mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    L, R = map(int, input().split())
    if L == 1:
        print(0)
        exit()
    ans = [1] * (R+1)
    for d in range(L, R+1):
        for j in range(2, R+1):
            if d*j > R:
                break
            ans[d*j] = 0
    ret = 0
    for i in range(L, R+1):
        if ans[i]:
            ret += 1
    print(ret)


if __name__ == '__main__':
    main()