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.

Input: Consider Input: Sentence1: Mammals depend on the vegetation for food and shelter. 
Sentence2: Mammals are Heterotrophs.

Output: Mammals


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

Output: frogs


Input: Consider Input: Sentence1: Biodiversity generally increases from the poles to the equator. 
Sentence2: diversity of life generally increases from the poles to the equator.


Output: equator