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: Humans have collected and grown mushrooms for food for thousands of years. 
Sentence2: Yeast and mushrooms are types of fungus.

Output: mushrooms


Input: Consider Input: Sentence1: Sound vibrations can be compared to pond ripples. 
Sentence2: dropping an object into water causes pond ripples.

Output: pond


Input: Consider Input: Sentence1: Gene flow occurs when individuals move into or out of a population. 
Sentence2: Internal migration describes moves within a country.


Output: move