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: Coral Reefs Coral reefs are widely distributed in warm shallow waters. 
Sentence2: warm shallow waters provide food and shelter to many ocean organisms.

Output: shallow


Input: Consider Input: Sentence1: a fire requires oxygen to burn. 
Sentence2: Oxygen has  eight protons and eight electrons.

Output: oxygen


Input: Consider Input: Sentence1: Roots grow in length and width from primary and secondary meristem. 
Sentence2: Most plants have roots .


Output: Roots