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: Interest in fossils is worldwide. 
Sentence2: paleontologists study something with worldwide interest.

Ex Output:
Interest


Ex Input:
Sentence1: Oil and gasoline are fossil fuels. 
Sentence2: lawn mowers convert fossil fuels into motion.

Ex Output:
fossil


Ex Input:
Sentence1: Shivering occurs when many muscles contract a little bit all at once. 
Sentence2: Shivering causes muscle contractions to warm the body.

Ex Output:

muscles