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.

Ex Input:
Sentence1: protein is used to repair cells by the human body. 
Sentence2: Meat, fish and chicken are rich sources of protein.

Ex Output:
protein


Ex Input:
Sentence1: high pressure systems cause clear weather. 
Sentence2: Weather Clear weather usually means good visibility.

Ex Output:
clear


Ex Input:
Sentence1: hiding can be used for avoiding predators. 
Sentence2: By avoiding outside weather extremes, the unit's life span is expanded.

Ex Output:

avoiding