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: Life without protein is impossible.

Ex Output:
proteins


Ex Input:
Sentence1: Echinoderms lack respiratory and excretory systems. 
Sentence2: echinoids lack a respiratory system.

Ex Output:
respiratory


Ex Input:
Sentence1: Insulin is a hormone that helps cells absorb sugar from the blood. 
Sentence2: the pancreas produces a hormone that helps cells absorb sugar from the blood.

Ex Output:

absorb