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: triceps contracting causes a person 's elbow to straighten. 
Sentence2: muscles contracting cause a person's elbow to straighten.

Ex Output:
contracting


Ex Input:
Sentence1: if an object in a fluid is more dense than that fluid then that object will sink in that fluid because of gravity. 
Sentence2: Most seeds are more dense than water.

Ex Output:
dense


Ex Input:
Sentence1: Digestion is the process of breaking down food into components the body can absorb. 
Sentence2: breaking down rice into components the body can absorb is digestion.

Ex Output:

Digestion