#!/usr/bin/perl
use strict;
use warnings;
use List::MoreUtils 'first_index';
my @terms = (); # Instructions
my @list = (); # AoA
my $last = undef; # last read.
while (my $line = <STDIN>) {
        chomp($line);
        # We need to reprocess all instructions to keep old orders
        push @terms, $line;
        foreach my $item (@terms) {
                if ($item eq 'Start') {
                        # nothing before start.
                        $last = undef;
                        next;
                }
                my ($last_position,$item_position);
                if (defined $last) {
                        ($last_position) = grep { grep { $_ eq $last } @{$_} } @list;
                }
                ($item_position) = grep { grep { $_ eq $item } @{$_} } @list;
                if ($last_position && !$item_position) {
                        my $idx = first_index { $_ == $last_position } @list;
                        $list[$idx+1] ||= [];
                        push @{$list[$idx+1]}, $item;
                } elsif ($last_position && $item_position) {
                        my $idx = first_index { $_ == $last_position } @list;
                        my $idx2 = first_index { $_ == $item_position } @list;
                        if ($idx == $idx2) {
                                # disambiguation
                                my $idx = first_index { $_ == $last_position } @list;
                                @{$last_position} = grep { $_ ne $item } @{$last_position};
                                $list[$idx+1] ||= [];
                                push @{$list[$idx+1]}, $item;
                        } elsif ($idx > $idx2) {
                                # complex disambiguation
                                @{$item_position} = grep { $_ ne $item } @{$item_position};
                                $list[$idx+1] ||= [];
                                push @{$list[$idx+1]}, $item;
                        }
                } elsif (!$last_position && !$item_position) {
                        $list[0] ||= [];
                        push @{$list[0]}, $item;
                }
                $last = $item;
        }
}

my @ambiguous = grep {defined $_->[1]} @list;
if (@ambiguous) {
        warn 'Ambiguous items: '.join ', ', map { join '|', @{$_} } @ambiguous;
}

print join ', ', map { join '|', @{$_} } @list;
print "\n";