use warnings;
use strict;

my @array = <>;
my @uniq= map {
    $_->[0]
} grep {
    ! $_->[1]
} sort {
    my $v = $a->[0] cmp $b->[0];
    $a->[1] = 1 unless $v or $b->[1];
    $v
} map {
    [$_]
} @array;

print @uniq;