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: Cells are the microscopic building blocks of organisms. 
Sentence2: proteins are the building blocks of organisms.

Ex Output:
organisms


Ex Input:
Sentence1: Interstellar space contains a plasma. 
Sentence2: interstellar space contains electrons, atoms, and stars.

Ex Output:
Interstellar


Ex Input:
Sentence1: using cell phones can cause people to become distracted. 
Sentence2: Using a cell phone when driving can lead to a lethal situation.

Ex Output:

cell