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: Mad Cow disease is a concern. 
Sentence2: pathogens can cause Mad Cow.

Ex Output:
Cow


Ex Input:
Sentence1: when electricity flows to a light bulb , the light bulb will turn on. 
Sentence2: water pumps can turn on light bulbs.

Ex Output:
bulb


Ex Input:
Sentence1: an animal requires nutrients to grow and heal. 
Sentence2: vitamin C helps animals heal.

Ex Output:

animal