Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

Ex Input:
Sentence1: Some pelycosaurs gave rise to a group of animals called therapsids. 
Sentence2: Like most other groups of synapsids, all pelycosaurs are now extinct.

Ex Output:
pelycosaurs


Ex Input:
Sentence1: Insects spread disease and destroy crops. 
Sentence2: Crops are plants that are grown for food or other uses.

Ex Output:
crops


Ex Input:
Sentence1: Birds have relatively large brains and a high level of intelligence. 
Sentence2: Class Aves is for the birds, literally.

Ex Output:

Birds