X under 1st post, Y under the rest

Hello,
I’m sure this is really simple but im pretty crap trying to figure out the php if else code.

Basically i want a specific unique sentence of text to be displayed under the first wordpress post on index.php

And for all the other posts on the index.php to have the same text underneath them.

Example:

First Post Title on Index.php
<blog text>
Why not subscribe to our RSS feed?

———————

All Other Post Titles on Index.php
<blog text>
Some boring text for all other entries