WP get first and last post title

WP get first and last post title

I am listing cities and order them alphabetically and I came up with this
code
<?php
$args=array(
'post_type' => 'cities',
'orderby' => 'title',
'order' => 'ASC',
'posts_per_page'=>-1,
'caller_get_posts'=>1
);
$my_query = new WP_Query($args);
if( $my_query->have_posts() ) {
while ($my_query->have_posts()) : $my_query->the_post();?>
<?php
$this_char = strtoupper(substr($post->post_title,0,1));
if ($this_char != $last_char) {
$last_char = $this_char;
if (isset($flag))
echo '</div>';
echo '<div data-role="collapsible" class="excerpts">';
echo '<h3 class="alphabet">'. '<div>'.$last_char. '</div>' .'</h3>';
$flag = true;
} ?>
<p class="inner"><a data-transition="slide" href="<?php the_permalink()
?>" rel="bookmark" title="Permanent Link to <?php
the_title_attribute(); ?>"><?php the_title(); ?></a></p>
<?php endwhile; }
if (isset($flag))
echo '</div>';
wp_reset_query();?>
This code generates the following HTML
<div class="collapsible">
<h3><div>A</div></h3>
<p>Atlanta</p>
<p>Alabama</p>
<p>Arizona</p>
</div>
but what I am trying to achieve is to have the first and last post title
next to the letter, something like this
<div class="collapsible">
<h3><div>A</div> Atlanta - Arizona</h3>
<p>Atlanta</p>
<p>Alabama</p>
<p>Arizona</p>
</div>
How can I get in wordpress the last post title? Any ideas? Thank You.
I tried this for the first but I don't know about the last
echo '<h3 class="alphabet">'. '<div>'.$last_char. '</div>' .
get_the_title() .' - get_the_last_title' .'</h3>';