<?php get_header(); ?>

    <div id="primary" class="content-area">
        <main id="main" class="site-main" role="main">

            <?php
            if (have_posts()) : while (have_posts()) : the_post();

                $custom_arr = array(1,2,3,4);
                if (in_array(get_the_ID(), $custom_arr)) {
                    get_template_part( 'parts/loop', 'single-custom' );
                }
                else {
                   get_template_part( 'parts/loop', 'single' );
                }

            endwhile; else :

                get_template_part( 'parts/content', 'missing' );

            endif;
            ?>
        </main><!-- #main -->
    </div><!-- #primary -->

<?php get_footer(); ?>