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

Ex Output:
thunderstorms


Ex Input:
Sentence1: Instead, the body is covered with a protective shell of bony armor. 
Sentence2: Most mollusks have protective of bony armor.

Ex Output:
armor


Ex Input:
Sentence1: bacteria cause food to spoil. 
Sentence2: Warmth and moisture can lead to spoiled food.

Ex Output:

food