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: 'small herd of goats running on unpaved road with three male onlooker'. Reverse all words of length '5' in the given sentence.

llams herd of staog running on unpaved road with eerht male onlooker