Ne pas devoir

Can anyone tell me why this example in my lesson is:

"Nous acheterons assez a manger pour ne pas devoir aller au restaurant"

when my logic tells me I want to put it this way:

"Nous acheterons assez a manger pour ne devrons pas aller au restaurant"

And I have rarely seen "ne pas" put together before  - I thought the rule was one in front of the verb and one after.

Can someone help?

Thank you!
 

When you have a verb in the infinitive, the two parts of the negation are placed before the verb. Ex: J'enlève mes chaussures pour ne pas faire du bruit dans la maison. (I take off my shoes to not make noise in the house.)

As to why it wasn't written the second way (Nous acheterons assez a manger pour ne devrons pas aller au restaurant), it's because it reads awkward in French to have the second conjugation like that instead of the infinitive. This is one of those instances where where you can't translate from the English, even if the translation makes sense in English. The latter structure has to be in form of "... to not have to leave."
 

Merci. Bonne explication.

I was looking for the explanation, it is clear to me now.    Here is a nice sentence with this style of negation from lesson 13.4.
Combien de fois je t'ai dit de ne pas laisser traîner tes affaires ?

Vit Novak