instruction:
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.
question:
A tw tone green train is being shown in a street mirror.
answer:
tw


question:
A steeet sign that is mounted to the side of a building.
answer:
steeet


question:
the asmall plane is hanging in a building
answer:

asmall