#!/usr/bin/perl

use strict;
use warnings;

use Graph::Directed;

my @array1= ( 1, 2, 3, 4);
my @array2= ( 5, 6, 7, 8);
my @array3= ( 9, 10, 11, 12);


my $graph = Graph::Directed->new;
$graph->add_path(@array1);
$graph->add_path(@array2);
$graph->add_path(@array3);


my @ordered = $graph->toposort();
print "@ordered";