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: Most fungi get organic compounds from dead organisms. 
Sentence2: Moulds, yeasts, rusts, smuts, mildews, and mushrooms are all types of fungi.

Ex Output:
fungi


Ex Input:
Sentence1: an animal requires air for survival. 
Sentence2: The Moon has no atmosphere and no air.

Ex Output:
air


Ex Input:
Sentence1: an animal requires warmth for survival. 
Sentence2: an animal requires heat produced by the body for survival.

Ex Output:

animal