def main1(l,r):
  if l==1:return 0
  g=[set() for _ in range(r-l+1)]
  for i in range(l,r+1):
    ii=i+i
    while ii<=r:
      g[ii-l].add(i-l)
      g[i-l].add(ii-l)
      ii+=i
  mi=set(range(r-l+1))
  ans=0
  while mi:
    ans+=1
    v0=mi.pop()
    todo=[v0]
    while todo:
      v=todo.pop()
      for nv in g[v]:
        if nv in mi:
          todo.append(nv)
          mi.discard(nv)
  return ans-1

if __name__=='__main__':
  l,r=map(int,input().split())
  ret1=main1(l,r)
  print(ret1)