[Haskell-beginners] Passing a file containing a list as an input

Hello everyone! I am really struggling with Haskell I/O. I have written a mergesort program and as an input to that program I want to use a file containing a list of 1000 integers. Let's say the contents of the file look like this [120, 400, 500 , 20, 100 ..] How can I achieve that? I am trying to write a main function that takes the file as an input and passes the list to my mergesort function.. Regards Awsaf Rahman