TIMEOUT
MAYBE
Trs:
 {top2(x, free(y)) -> top1(new(x), check(y)),
  top2(x, free(y)) -> top1(check(new(x)), y),
  top2(x, free(y)) -> top1(check(x), new(y)),
  top2(x, free(y)) -> top1(x, check(new(y))),
  top1(free(x), y) -> top2(new(x), check(y)),
  top1(free(x), y) -> top2(check(new(x)), y),
  top1(free(x), y) -> top2(check(x), new(y)),
  top1(free(x), y) -> top2(x, check(new(y))),
      new(serve()) -> free(serve()),
      new(free(x)) -> free(new(x)),
    check(free(x)) -> free(check(x)),
     check(new(x)) -> new(check(x)),
     check(old(x)) -> old(check(x)),
     check(old(x)) -> old(x),
      old(serve()) -> free(serve()),
      old(free(x)) -> free(old(x))}
 Open