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: Nitrogen is found in proteins, nucleic acids, and chlorophyll. 
Sentence2: Lawns eat nitrogen.

Ex Output:
Nitrogen


Ex Input:
Sentence1: cold fronts cause thunderstorms as they pass by. 
Sentence2: Thunderstorms create havoc.

Ex Output:
thunderstorms


Ex Input:
Sentence1: Meter sticks have units called centimeters and millimeters. 
Sentence2: Centimeters and millimeters are units of distance.

Ex Output:

centimeters