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: If there is sun, there is sunlight, there is day. 
Sentence2: Energy enters ecosystems from the sun.

Output: sun


Input: Consider Input: Sentence1: Insulin is a hormone that helps cells absorb sugar from the blood. 
Sentence2: the pancreas produces a hormone that helps cells absorb sugar from the blood.

Output: absorb


Input: Consider Input: Sentence1: a flower 's purpose is to produce seeds. 
Sentence2: A flower's job is to produce seeds.


Output: 's