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: Heterotrophs are living things that cannot make their own food. 
Sentence2: food contains organic molecules.

Ex Output:
food


Ex Input:
Sentence1: Passive immunity lasts only as long as the antibodies survive in body fluids. 
Sentence2: Passive immunity diminishes with time.

Ex Output:

Passive