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: Plants exhibit phototropism, or growing toward a light source. 
Sentence2: Bamboos are vigorous, rugged plants.

Ex Output:
Plants


Ex Input:
Sentence1: All frogs are amphibians. 
Sentence2: frogs have permeable skin that easily absorbs substances from the environment.

Ex Output:
frogs


Ex Input:
Sentence1: Wet dreams are a sign of puberty. 
Sentence2: Wet dreams are a sign of sexually maturity.

Ex Output:

Wet