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.

Input: Consider Input: Sentence1: a battery converts chemical energy into electrical energy. 
Sentence2: A battery produces a flow of electrons.

Output: battery


Input: Consider Input: Sentence1: a flashlight converts chemical energy into light energy. 
Sentence2: Only as long as there are batteries in the flashlight, the flashlight will function.

Output: flashlight


Input: Consider Input: Sentence1: Electrical energy refers to energy associated with the flow of electrons. 
Sentence2: a light bulb requires the flow of electrons to produce light.


Output: electrons