Monitor display is upside down

Dear All,
I am having trouble with my home computer. I leaned on our window to check someone who called me from outside the house and when I get back to my computer, I found out that my monitor display is already upside down. Yeah, I think I have pressed something on the computer to make the display like that, but I want to get it back to what it was before. I was told to press Control + Alt + Up Arrow Key, but sadly, that does not work. I do not know any other options to try aside from that step that fixed my issue before.
Thanks in Advance,
Mike
