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: Most bryophytes are small. 
Sentence2: Most in the same group as mosses are small.

Ex Output:
small


Ex Input:
Sentence1: heating an egg causes a chemical reaction in the egg. 
Sentence2: Insects hatch from eggs.

Ex Output:
egg


Ex Input:
Sentence1: coal is used to produce electricity by burning in coal-fire power stations. 
Sentence2: Coal produces electricity by being heated up in coal-fire power stations.

Ex Output:

coal