Definition: In this task, you need to remove 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: 'people on motorcycles decorated in american flags riding down the street with people watching from the sidewalk area'. Remove all words of length '4' in the given sentence.

people on motorcycles decorated in american flags riding the street people watching the sidewalk