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

Output: chemical


Input: Consider Input: Sentence1: For instance, glucose is a sugar. 
Sentence2: insulin helps cells take up sugar from the blood.

Output: sugar


Input: Consider Input: Sentence1: a mutation in the sex cells of a parent can cause a new trait to appear in the parent 's offspring. 
Sentence2: mutation in the sex cells of a parent can help the offspring survive.


Output: cells