((
  open(d11),
  move(r1, c1),
  close(d11)
  open(dc),
  move(c1, c2),
  close(dc),
  open(d23),
  move(c2, r3),
  close(d23),
  open(d23),
  move(r3, c2),
  close(d23),
  open(d24),
  move(c2, r4),
  move(r4, c2),
  close(d23),
  open(dc),
  move(c2, c1),
  close(dc),
  open(d11),
  move(c1, r1),
  close(d11),
  wait()
 ),
 0
)