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: a switch is used to start the flow of current in an electrical circuit. 
Sentence2: The flow of electrical current powers a light bulb.

Ex Output:
current


Ex Input:
Sentence1: Some trees are maples. 
Sentence2: planting maples has a positive impact on an ecosystem.

Ex Output:
maples


Ex Input:
Sentence1: Common micro-organisms include fungi and bacteria. 
Sentence2: Common micro-organisms can cause people to become ill.

Ex Output:

Common