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: when electricity flows to a light bulb , the light bulb will turn on. 
Sentence2: water pumps can turn on light bulbs.

Ex Output:
bulb


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

Ex Output:
maples


Ex Input:
Sentence1: Fish is available in the rivers and lakes of the district in large quantities. 
Sentence2: Habitats where fish live in large quantities are usually larger than streams.

Ex Output:

Fish