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: Visible and invisible light is energy in the form of electromagnetic waves. 
Sentence2: Eyes are used for seeing animals by sensing electromagnetic waves.

Output: electromagnetic


Input: Consider Input: Sentence1: Eggs are usually laid in a nest. 
Sentence2: birds have nests.

Output: nest


Input: Consider Input: Sentence1: astronauts require preserved food for extended flights. 
Sentence2: astronauts require canned food for extended flights.


Output: astronauts