How to turn . $page . into a variable

I have this code in my sidebar:

<?php
$output = wp_list_pages('echo=0&depth=1&title_li=<h2>Main Menu </h2>&exclude=73' );
if (is_page( )) {
  $page = $post->ID;
  if ($post->post_parent) {
    $page = $post->post_parent;
  }
  $children=wp_list_pages( 'echo=0&child_of=' . $page . '&title_li=' );
  if ($children) {
    $output = wp_list_pages ('echo=0&child_of=' . $page . '&title_li=<h2>' . __('Menu') . '</h2>');
  }
}
echo $output;
?>

The last . $page . returns the id number id of the page where I need it to return the title of the page. What do I do? Any help will be greatly appreciated. Thanks.