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: An astronaut is a scientist who is a space explorer. 
Sentence2: Space explorers require preserved food for long flights.

Output: explorer


Input: Consider Input: Sentence1: skin is used for protecting the body from harmful substances. 
Sentence2: Acids are harmful to tissue.

Output: harmful


Input: Consider Input: Sentence1: Frogs are a type of reptile. 
Sentence2: frogs produce amniotic eggs.


Output: Frogs