A PuZzLe tO SoLvE

Being so bored with no boss around today, my colleague gave me a puzzle to solve. And I find that its a challenge to me wor. Zitao my brain dio blocked after some calculations. Freaking make me think until gonna kisiao liaoz. Anyway, you all also go try this puzzle ba. Got answer one hor. See whether there's any genius here who can come up with the answer. Share with us the answer and how you got it in the Comment section. Best of luck!

MATHEMATICS PUZZLE

THERE IS ONE BUS, INSIDE THE BUS THERE ARE 7 GIRLS, EACH GIRL HAS 7 BAGS.
INSIDE EACH BAG THERE ARE 7 CATS, EACH CAT HAS 7 SMALL CATS.
HOW MANY NIPPLES ARE THERE INSIDE THE BUS?

PLEASE NOTE THAT THE CAT ALSO HAS 7 NIPPLES EACH.