#! perl -slw
use strict;
use Algorithm::Combinatorics qw[ combinations ];

my $favourite = 1009;
my $n = <>;
my %pairings;
push( @{ $pairings{ $_->[0] } }, $_->[1] ),
push( @{ $pairings{ $_->[1] } }, $_->[0] ),
    while @{ $_ = [split ' ', <> ] };

my @ids = keys %pairings;

my %idPos; @idPos{ @ids } = 0 .. @ids;
my %posId; @posId{ values %idPos } = keys %idPos;

my @masks;
for my $id ( @ids ) {
    $masks[ $idPos{ $id } ] = '';
    vec( $masks[ $idPos{ $id } ], $idPos{ $id }, 1 ) = 1;
    vec( $masks[ $idPos{ $id } ], $idPos{ $_  }, 1 ) = 1
        for @{ $pairings{ $id } };
}

my @hits;
for my $k ( 1 .. $n ) {
    my $iter = combinations( [0 .. $#ids], $k );
    while( my $c = $iter->next ) {
        my $ored = '';
        $ored |= $masks[ $_ ] for @$c;
        my $count = unpack '%32b*', $ored;
        push @hits, [ $k, @$c ] if $count >= @ids;
    }
    last if @hits;
}

if( @hits > 1 ) {
    @hits = sort{ $a->[0] <=> $b->[0] } @hits;
    my $min = $hits[0][0];
    my $i = $#hits;
    --$i while $hits[ $i ][0] > $min;
    $#hits = $i;
    if( @hits > 1 ) {
        my $first = $hits[ 0 ];
        @hits = grep {
            scalar grep{
                $posId{ $_ } == $favourite;
            } @$_[ 0 .. $#{ $_ } ];
        } @hits;
        @hits = @hits >= 1 ? $hits[ 0 ] : $first;
    }
}

print @{ $hits[0] } -1;
print $posId{ $_ } for @{ $hits[0] }[ 1 .. $#{ $hits[ 0 ] } ];