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 gray tiger stripe cat laying on top of a wooden bench'. Reverse all words of length '6' in the given sentence.

a gray tiger epirts cat gniyal on top of a nedoow bench