What do you say... I NEED AN ANSWER QUICK!!!!?

Ok, so this dude I dont even know on facebook says: wat lil sexii. and i say: ummm EXCUSE YOU?! And he says: wat your num lil cutie. what do I say? HELP!! I dont even know the dud enad i need something good to say to him!! example: get a life!! Thats not a good one so i need QUICK help!!