#!/usr/bin/perl

use strict;
use warnings;

$\ = $, = "\n";
chomp(my $head=<>);

my ($last,@buffer);
while (<>) {
    chomp;
    my $time = (split)[0];
    if ( $time eq ($last ||= $time) ) {
        push @buffer, $_;
    } else {
        print $head, @buffer;
        ($last,@buffer)=($time,$_);
    }
}
print $head, @buffer;

__END__