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: 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: Mollusks are invertebrates such as the common snail. 
Sentence2: Another common snail is the decollate snail.

Ex Output:
snail


Ex Input:
Sentence1: a spider web is used to capture food by spiders. 
Sentence2: tool extensions are used to capture food by spiders.

Ex Output:

capture