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: Scientists still know relatively little about Archaea. 
Sentence2: scientists still know relatively little about non-bacterial prokaryotes.

Ex Output:
Scientists


Ex Input:
Sentence1: faulting of rock in Earth 's crust causes earthquakes. 
Sentence2: fault movement forms earthquakes.

Ex Output:
earthquakes


Ex Input:
Sentence1: an animal requires nutrients for survival. 
Sentence2: Potassium is important for an animal to survive.

Ex Output:

survival