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: Insect wings are attached to the dorsal side of their thorax. 
Sentence2: wings are attached to the dorsal side of the insect.

Ex Output:
dorsal


Ex Input:
Sentence1: dropping an object into water causes vibrations in the water. 
Sentence2: Dropping an object into lake causes vibrations.

Ex Output:

dropping