TRS:
 {   msort(nil()) -> nil(),
   msort(.(x, y)) -> .(min(x, y), msort(del(min(x, y), .(x, y)))),
    min(x, nil()) -> x,
  min(x, .(y, z)) -> if(<=(x, y), min(x, z), min(y, z)),
    del(x, nil()) -> nil(),
  del(x, .(y, z)) -> if(=(x, y), z, .(y, del(x, z)))}
 Fail