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: an automobile engine transforms chemical energy into mechanical energy. 
Sentence2: cars transform chemical energy into mechanical energy.

Ex Output:
chemical


Ex Input:
Sentence1: wiring requires an electrical conductor. 
Sentence2: Gold is an excellent conductor of electricity.

Ex Output:
conductor


Ex Input:
Sentence1: Endospores are commonly found in soil and water. 
Sentence2: Some bacteria form resistant cells called endospores.

Ex Output:

Endospores