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: Mammalian teeth are important for digestion. 
Sentence2: bats' teeth are important for digestion.

Ex Output:
digestion


Ex Input:
Sentence1: Lancelet larvae are free-swimming. 
Sentence2: some larvae lack a hardened backbone.

Ex Output:
larvae


Ex Input:
Sentence1: Food is the best source of nutrients for the body. 
Sentence2: The small intestine is the main place where food absorption occurs.

Ex Output:

Food