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: bacteria can cause people to become ill. 
Sentence2: bacteria can cause people to die.

Output: bacteria


Input: Consider Input: Sentence1: friction is used for stopping a vehicle by brakes. 
Sentence2: friction is used for stopping a car by brakes.

Output: brakes


Input: Consider Input: Sentence1: Sound waves vibrate. 
Sentence2: a firecracker converts chemical energy into vibrating waves.


Output: vibrate