Definition: In this task, you need to reverse all words of a given length in the sentence. The number of letters in a word determine its length. For example, the length of the word "apple" is 5.
Input: Sentence: 'a man standing in the snow and his skis a standing on end with his helmet on top of them'. Reverse all words of length '3' in the given sentence.

a nam standing in eht snow dna sih skis a standing on dne with sih helmet on pot of them