def find(x):
    if data[x] < 0:
        return x
    data[x] = find(data[x])
    return data[x]

def union(x, y):
    x, y = find(x), find(y)
    if x == y:
        return
    if data[x] > data[y]:
        x, y = y, x
    data[x] += data[y]
    data[y] = x

L, R = map(int, input().split())
MAX = 2 << 17
data = [0] * MAX
for i in range(L, R + 1):
    data[i] = -1
for u in range(L, R + 1):
    for v in range(2 * u, R + 1, u):
        union(u, v)
print(len(list(filter(lambda x: x < 0, data))) - 1)