How do i change my display name on facebook?

okay i went to account;; clicked account settings;; clicked 'change name' but when i try to change my display name it only has a drop down arrow thing and wheni click it it gives me the choice of my first and last name or my last name and then my first name... i wanna make it my first and middle name. how do i do this??How do i change my display name on facebook?
Make your middle name as your last name....And then in the full name option write this correctly.....Thus you'll show in your profile what your actual name is and at the same time you'll have your requirement fulfilled about display name........Except this no other way unfortunately :-(