Keyboard doesn't work and now I need to do a factory reset!

So my keyboard stopped working a few months ago and i've been using a 'dell' usb one since, but now my macbook seems to have died, it wont load past the grey screen and I can't seem to boot into safemode because of the keyboard being connected via usb? I don't mind losing all my documents, I just want to factory reset my macbook.

Any help would be massively appreciated, cheers.