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: For instance, glucose is a sugar. 
Sentence2: insulin helps cells take up sugar from the blood.

Ex Output:
sugar


Ex Input:
Sentence1: threatening behavior by predators causes a porcupine to extend its quills. 
Sentence2: Fishers are predators that can eat porcupines.

Ex Output:
predators


Ex Input:
Sentence1: Ancestors of hagfish are thought to have been the earliest vertebrates. 
Sentence2: Descendants of the early jawless fish are present today in the lampreys and hagfishes.

Ex Output:

hagfish