The given sentence contains a typo which could be one of the following four types: (1) swapped letters of a word e.g. 'niec' is a typo of the word 'nice'. (2) missing letter in a word e.g. 'nic' is a typo of the word 'nice'. (3) extra letter in a word e.g. 'nicce' is a typo of the word 'nice'. (4) replaced letter in a word e.g 'nicr' is a typo of the word 'nice'. You need to identify the typo in the given sentence. To do this, answer with the word containing the typo.

Q: Teenagers skateboard on the concrete outside a commercial buildoing.

A: buildoing.
****
Q: Chikldren are at the zoo by the giraffes.

A: Chikldren
****
Q: A group of four skiers and snowboarders standing on a mountain sloe.

A:
sloe.
****