Hi, I have a problem: Factor a^2-x^2-a-x

I know what the answer is, but I don't understand how to get there...

I get as far as taking out the difference of two squares

(a+x)(a-x)-a-x

and now I'm lost as how to continue to get the answer which is (a+x)(a-x+1) it looks simple, but I'm baffled!