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: hearing is used for sensing sound by animals. 
Sentence2: functioning ears are used for sensing sound by animals.

Ex Output:
animals


Ex Input:
Sentence1: freezing means changing from a liquid into a solid by reducing heat energy. 
Sentence2: Water freezes into ice when cooled.

Ex Output:
freezing


Ex Input:
Sentence1: bad weather decreases visibility while driving. 
Sentence2: Bad weather makes collisions more likely while driving.

Ex Output:

bad