COMPARING SENTENCES WITH INFINITIVES
Jim doesn't speak very clearly.
A.  It is difficult to understand him.
B.  He is difficult to understand.
Sentences A and B have the same meaning. But note that we say He is difficult to understand, not He is difficult to understand him.

You can use the structure in sentence B after difficult, easy, impossible, hard and after a few other adjectives. Let's see some examples:
- Your writing is almost impossible to read, not ...to read it.
(= It is almost impossible to read your writing)
- Do you think this water is safe to drink?, not ...to drink it?
- Adolfo is very interesting to talk to, not ...to talk to him.

You can also use this structure with an adjective + noun:
- This is a very difficult question to answer, not ...to answer it.
- Adolfo is an interesting person to talk to.
- I enjoyed the soccer game. It was an exciting game to watch on TV.

THE FIRST, THE  SECOND,  THE THIRD...
We use the infinitive after the first, the second, the third, etc., and also after the next and the last:
- Who was the first person to reach the South Pole?
- If I have any more news, you'll be the first to know.
- The next plane to arrive at gate 15 will be Flight 566 from Bariloche.
- Who was the last person to leave OM Personal building last night?