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: cell division often causes growth. 
Sentence2: Cell division leads to reproduction.

Ex Output:
cell


Ex Input:
Sentence1: Introns are regions that do not code for proteins. 
Sentence2: regions that do not code for proteins are removed by RNA splicing.

Ex Output:
code


Ex Input:
Sentence1: Scientists who find and study fossils are called paleontologists. 
Sentence2: Interest in fossils is worldwide.

Ex Output:

fossils