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: Ozone depletion results in higher levels of UV radiation reaching Earth. 
Sentence2: less ozone means more ultraviolet light.

Ex Output:
Ozone


Ex Input:
Sentence1: Animals can communicate with sounds, chemicals, or visual cues. 
Sentence2: cats can communicate with sounds, chemicals or visual cues.

Ex Output:
chemicals


Ex Input:
Sentence1: gravity causes objects that have mass to be pulled down on a planet. 
Sentence2: Another name for Mars is the Red Planet.

Ex Output:

planet