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: Carpools and vanpools can save time. 
Sentence2: vanpools decrease the amount of cars used to travel to a place.

Ex Output:
vanpools


Ex Input:
Sentence1: Bivalves feed on plankton and nonliving organic matter. 
Sentence2: Clams feed on plankton and nonliving organic matter.

Ex Output:
feed


Ex Input:
Sentence1: Nephrons are the structural and functional units of the kidneys. 
Sentence2: Mammalian kidneys form urine in nephrons.

Ex Output:

Nephrons