class UnionFind:
  def __init__(self, n):
    self.node = [-1 for _ in range(n)]

  def root(self, v):
    if self.node[v] < 0:
      return v

    st = []
    while self.node[v] >= 0:
      st.append(v)
      v = self.node[v]

    for u in st:
      self.node[u] = v

    return v

  def size(self, v):
    v = self.root(v)
    return (- self.node[v])

  def same(self, u, v):
    return self.root(u) == self.root(v)

  def unite(self, u, v):
    ru = self.root(u)
    rv = self.root(v)
    if ru == rv:
      return

    du = self.node[ru]
    dv = self.node[rv]
    if du <= dv:
      self.node[rv] = ru
      self.node[ru] += dv
    else:
      self.node[ru] = rv
      self.node[rv] += du

l, r = map(int, input().split())
offset = - l

uf = UnionFind(r - l + 1)
for x in range(l, r + 1):
  for y in range(2 * x, r + 1, x):
    uf.unite(x + offset, y + offset)

cnt = {}
for v in range(r - l + 1):
  r = uf.root(v)
  cnt[r] = cnt.get(r, 0) + 1

print(len(cnt) - 1)