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: Dilation occurs when cell walls relax. 
Sentence2: Decreased oxygen levels cause blood vessels to dilate and cell walls to relax.

Output: relax


Input: Consider Input: Sentence1: Babies that are very large or very small at birth are less likely to survive. 
Sentence2: Babies that are very large or very small at birth are less likely to live.

Output: Babies


Input: Consider Input: Sentence1: mountains are formed by earthquakes. 
Sentence2: Japan has a lot of mountains.


Output: mountains