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: if an object is kicked then force is exerted on that object. 
Sentence2: if an object is kicked then a measurement of newtons is exerted on that object.

Ex Output:
exerted


Ex Input:
Sentence1: Energy enters ecosystems in the form of sunlight or chemical compounds. 
Sentence2: Energy enters ecosystems in the form of photons.

Ex Output:
Energy


Ex Input:
Sentence1: eyes are used for seeing by animals by sensing light. 
Sentence2: Nocturnal animals' eyes are very sensitive and used for seeing.

Ex Output:

seeing