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: All sharks are predators. 
Sentence2: hiding can be used for avoiding sharks.

Ex Output:
sharks


Ex Input:
Sentence1: a flower 's purpose is to produce seeds. 
Sentence2: Every job has meaning and purpose.

Ex Output:
purpose


Ex Input:
Sentence1: bacteria can cause people to become ill. 
Sentence2: Leptospirosis can cause people to become ill.

Ex Output:

become