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

Ex Output:
seismometer


Ex Input:
Sentence1: All monkeys are mammals. 
Sentence2: monkeys conserve body heat with their hair or fur.

Ex Output:
monkeys


Ex Input:
Sentence1: Coral reefs provide food and shelter to many ocean organisms. 
Sentence2: Coral reefs provide food and shelter to many fish.

Ex Output:

Coral