produce(n)
  i = 2
  while( i < n )
    send p2 i
    i = i + 1
  send p2 -1

consume()
  flag = 1
  while flag
    m = receive p1
    if( m < 0 )
      flag = 0
  print("\n")

main()
  p1 = run(produce(1000))
  p2 = run(consume())