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: Weather Clear weather usually means good visibility. 
Sentence2: High pressure systems can cause good visibility.

Output: good


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: Propulsion means to push forward or drive an object forward. 
Sentence2: A push forward is used for flying by a spacecraft.


Output: forward