I'll give you a hint..... It's NOT 13, my lucky number......
EDIT
I honestly can't believe only a handful of people want a free Tshirt..
I figured this would be full of numbers.....
how am i cheating>? it wasn't a "multipost.... more like a tri-post.... , the rules never stated that i only got one guess, nor that i couldn't guess a few times in a row... just want to see a win, not very many guesses here... what fun's a contest if no one wins?