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: 'one man in a red hat is talking on his cell phone and the other man is holding an umbrella and is facing the man on the phone'. Reverse all words of length '1' in the given sentence.

one man in a red hat is talking on his cell phone and the other man is holding an umbrella and is facing the man on the phone