#!/usr/bin/perl
use strict;

my @list1 = qw/ 1 2 3 4 5 6 /;
my @list2 = qw/ 6 2 1 5 4 3 /;
my @list3 = qw/ 7 1 6 5 4 3 /;
my @list4 = qw/ 4 5 7 6 2 3 /;
my @list5 = qw/ 0 4 5 6 2 3 /;

printf "%s\n", validate_number_list (\@list1) ? "Ok" : "Error";
printf "%s\n", validate_number_list (\@list2) ? "Ok" : "Error";
printf "%s\n", validate_number_list (\@list3) ? "Ok" : "Error";
printf "%s\n", validate_number_list (\@list4) ? "Ok" : "Error";
printf "%s\n", validate_number_list (\@list5) ? "Ok" : "Error";

sub validate_number_list()
{
    my ($list) = @_;
    my @sorted_list = sort { $a <=> $b } @{$list};
    my $prev;
    foreach (@sorted_list)
    {
    	$prev + 1 != $_ ? return(0) : {$prev = $_};
    }
    return 1;
}