Instructions: 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: 'a large flock of birds flying over a field next to a  tree'. Remove all words of length '2' in the given sentence.
Output:
a large flock birds flying over a field next a tree