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: sonar is used to find the location of an object. 
Sentence2: Surface ships use sonar to locate and track submarines.

Output: location


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: Bears use the fat as energy over the winter hibernation. 
Sentence2: bears hibernate to conserve energy.


Output: Bears