swl_pp2 => sub {
        my @list = @input;
        @list = sort {$a<=>$b} @list;
        if ($list[0] < 0 && $list[-1] >= 0) {
            my $i = 0; $i++ while ($list[$i]<0);
            push @list, splice @list, 0, $i;
        }
        Compare(\@list,\@output) or die "@list" if DO_CHECK;
    },