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.

Input: Consider Input: Sentence1: Limestone caves displaying stalactites. 
Sentence2: Limestone caves are formed by depositions.

Output: Limestone


Input: Consider Input: Sentence1: boiling means change from a liquid into a gas by adding heat energy. 
Sentence2: boiling changes a liquid into steam.

Output: liquid


Input: Consider Input: Sentence1: Another symbolic object is the badge on the hat of Dinteville. 
Sentence2: if two balanced forces act on an badge in opposite directions then that badge will remain stationary.


Output: badge