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.

Example Input: A tw tone green train is being shown in a street mirror.
Example Output: tw

Example Input: a mab holds a box of doughnuts as he smiles
Example Output: mab

Example Input: Thrre giraffes stand in the grass by a dirt pile.
Example Output:
Thrre