function twentyfourteen_the_attached_image() {
    $post = get_post();
    
/**
 * Filters the default Twenty Fourteen attachment size.
 *
 * @since Twenty Fourteen 1.0
 *
 * @param array $dimensions {
 *     An array of height and width dimensions.
 *
 *     @type int $height Height of the image in pixels. Default 810.
 *     @type int $width  Width of the image in pixels. Default 810.
 * }
 */
    $attachment_size     = apply_filters( 'twentyfourteen_attachment_size', array( 810, 810 ) );
    $next_attachment_url = wp_get_attachment_url();

    /*
		 * Grab the IDs of all the image attachments in a gallery so we can get the URL
		 * of the next adjacent image in a gallery, or the first image (if we're
		 * looking at the last image in a gallery), or, in a gallery of one, just the
		 * link to that image file.
		 */
    $attachment_ids = get_posts(
      array(
        'post_parent'    => $post->post_parent,
        'fields'         => 'ids',
        'numberposts'    => -1,
        'post_status'    => 'inherit',
        'post_type'      => 'attachment',
        'post_mime_type' => 'image',
        'order'          => 'ASC',
        'orderby'        => 'menu_order ID',
      )
    );

    // If there is more than 1 attachment in a gallery...
    if ( count( $attachment_ids ) > 1 ) {
      foreach ( $attachment_ids as $idx => $attachment_id ) {
        if ( $attachment_id == $post->ID ) {
          $next_id = $attachment_ids[ ( $idx + 1 ) % count( $attachment_ids ) ];
          break;
        }
      }

      if ( $next_id ) {
        // ...get the URL of the next image attachment.
        $next_attachment_url = get_attachment_link( $next_id );
      } else {
        // ...or get the URL of the first image attachment.
        $next_attachment_url = get_attachment_link( reset( $attachment_ids ) );
      }
    }

    printf(
      '<a href="%1$s" rel="attachment">%2$s</a>',
      esc_url( $next_attachment_url ),
      wp_get_attachment_image( $post->ID, $attachment_size )
    );
  }