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: Every photograph is produced by a camera. 
Sentence2: Photographers record images.

Output: photograph


Input: Consider Input: Sentence1: an animal requires air for survival. 
Sentence2: The Moon has no atmosphere and no air.

Output: air


Input: Consider Input: Sentence1: a seismometer is used to measure the strength or magnitude of an earthquake. 
Sentence2: Seismometer Calibration : Instructions on how to calibrate a homemade seismometer.


Output: seismometer