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

Ex Output:
good


Ex Input:
Sentence1: intense heat has a negative impact on an organism. 
Sentence2: intense heat has a negative impact on plants.

Ex Output:
heat


Ex Input:
Sentence1: Fourty percent of biomass is carbon. 
Sentence2: organisms are mostly made out of carbon.

Ex Output:

carbon