show code only in part 1

thing is, i wanna show this code only in the “page 1” of my posts.

How is pagination slug working for your posts?

1. site.com/hello-world/page/1/

$url = $_SERVER["REQUEST_URI"]/* or get_the_permalink() for single posts*/;
if(strpos($url,"page/") != '' && strpos($url,"page/1" ) != '')
	echo "Let's do it!";

2. site.com/hello-world?page=1

if(!isset($_GET["page"]) || isset($_GET["page"]) && $_GET["page"] == "1")
	echo "Let's do it!";

Oh. then maybe this would work:

global $post;
$url = $_SERVER["REQUEST_URI"]/* or get_the_permalink() for single posts*/;
if($url == home_url( '/' ).$post->post_name || strpos($url,$post->post_name."/1" ) != '')
	echo "Let's do it!"; // do something here, condition: request uri is site.com/hello-world/ or  site.com/hello-world/1/ only, so site.com/hello-world/2/ and other pages are eliminated

Let me know how it goes.