CI 2.x->3.x file name changes cause url not work

i'm trying to upgrade CI from 2.2.6 to 3.0.0, i see that i will be changing all controller filename, E.g:
old:
application/controllers/land.php
change to:
application/controllers/Land.php

it will cause the url not work, cannot visit http://xxx.xxx.com/land as before, can only visit http://xxx.xxx.com/Land now
also for all ajax not work.

question:
how can i make my url unchange?