include some text in the begin of content

I have this code on file fuctions.php.

function diww_add_post_content($content) {
	if (is_single() || is_page()) {
		$content .= '<br><p><div id="newsletter-box terms">? ?????????? ???? ???????????? ?????????. ???????? ???????? ????  <a title="???? ??????." href="">????? ??????</a></div></p>';
	}
	return $content;
}
add_filter ('the_content', 'diww_add_post_content', 0);

It is for the end of the content.
How can i make it to show in the begin of the content. pages and posts?
Thanks a lot