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 flashlight converts chemical energy into light energy. 
Sentence2: Chemical energy converted to light energy requires batteries.

Output: chemical


Input: Consider Input: Sentence1: rocks interacting with wind over long periods of time causes weathering. 
Sentence2: When a rock undergoes erosion and weathering, it breaks down to form sediments.

Output: weathering


Input: Consider Input: Sentence1: a meter stick is used to measure distance. 
Sentence2: Depths and distances are represented in meters.


Output: distance