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: Carpools and vanpools can save time. 
Sentence2: vanpools decrease the amount of cars used to travel to a place.

Ex Output:
vanpools


Ex Input:
Sentence1: friction causes the temperature of an object to increase. 
Sentence2: Friction causes the temperature of a toy to increase.

Ex Output:
causes


Ex Input:
Sentence1: when an animal moves , chemical energy is converted to mechanical energy. 
Sentence2: when dogs move, chemical energy is converted to mechanical energy.

Ex Output:

chemical