problem with the page and subpage

hello i use satorii theme and it list all the pages and childpages. but i only want it to show main pages.

the code is here:

<?php 

	if ( count($post->ancestors) === 0 ) //if it's a top-level page, we'll show all it's children
	{
		echo  substr(wp_list_pages('sort_column=menu_order&child_of=' . $post->ID .'&echo=0&title_li=<h3 class="page-links-title">' . get_the_title($post->ID) . '</h3>'), 20, -5);
	} elseif ( count($post->ancestors) === 1 )  //if it's a second level, we'll show all its parents' children
	{
		echo substr(wp_list_pages('sort_column=menu_order&child_of=' . $post->ancestors[0] . '&echo=0&title_li=<h3 class="page-links-title">' . get_the_title($post->ancestors[0]) . '</h3>'), 20, -5);
	} else //if page it's more than two levels deep, we'll show all of its top-level ancestor's children
	{
		echo substr(wp_list_pages('sort_column=menu_order&child_of=' . $post->ancestors[1] . '&echo=0&title_li=<h3 class="page-links-title">' . get_the_title($post->ancestors[1]) . '</h3>'), 20, -5);
	}

?>

i have tried lots of variation but i cant solve it ??