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: Coral Reefs Coral reefs are widely distributed in warm shallow waters. 
Sentence2: warm shallow waters provide food and shelter to many ocean organisms.

Ex Output:
shallow


Ex Input:
Sentence1: After a seed is planted it is watered. 
Sentence2: seeds need water.

Ex Output:
seed


Ex Input:
Sentence1: Viruses cause many human diseases. 
Sentence2: Influenza causes human disease.

Ex Output:

diseases