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: Fractures heal when osteoclasts form new bone. 
Sentence2: Fractures A fracture is a broken or cracked bone.

Output: Fractures


Input: Consider Input: Sentence1: Lions live in social groups called prides. 
Sentence2: Chimpanzees live in social groups called communities.

Output: groups


Input: Consider Input: Sentence1: forming coal requires decaying vegetation. 
Sentence2: Energy resources include coal and petroleum.


Output: coal