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: Among families with children the average number of offspring is 1.8. 
Sentence2: information in an organism's chromosomes cause genetic traits to be passed down to that organism's children.

Ex Output:
children


Ex Input:
Sentence1: fluoride decreases tooth decay. 
Sentence2: tap water decreases tooth decay.

Ex Output:

decreases