#!/usr/bin/env perl

use strict;
use warnings;
use List::MoreUtils qw/uniq/;
use feature qw/state say/;

my $friend_id = 1009;
my %seen;
my @teams;
my @reps;

while (<>) {
  chomp;
  state $count = 0;
  if($count > 0) {
    my $pair = make_pair($_);
    $seen{$pair->[0]}++;
    $seen{$pair->[1]}++;
    push @teams, $pair
  }
  $count++;
}

LINE: for my $pair (@teams) {
  my ($first, $second) = ($pair->[0], $pair->[1]);
  if($seen{$first} >= 2) {
    push @reps, $first;
    next LINE;
  } 
  elsif($seen{$second} >= 2) {
    push @reps, $second;
    next LINE;
  }
  else {
    $second == 1009
    ? push @reps, $second
    : $first == 1009
    ? push @reps, $first
    : push @reps, $first;
  }
}

my @result = uniq @reps;
say scalar @result;
say for @result;

sub make_pair {
  ## Str -> ArrayRef
  my $s = shift;
  my @pair = split / /, $s;
  \@pair;
}