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: bacteria can cause people to become ill. 
Sentence2: bacteria can cause people to die.

Ex Output:
bacteria


Ex Input:
Sentence1: Competition may lead to aggressive behaviors or displays of aggression. 
Sentence2: Aggression Aggression and violence often go together.

Ex Output:
aggression


Ex Input:
Sentence1: Some pelycosaurs gave rise to a group of animals called therapsids. 
Sentence2: Some pelycosaurs gave rise to reptiles ancestral to mammals.

Ex Output:

Some