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: Oil and gasoline are fossil fuels. 
Sentence2: lawn mowers convert fossil fuels into motion.

Output: fossil


Input: Consider Input: Sentence1: a plant requires sunlight to grow. 
Sentence2: Grass needs air and sunlight.

Output: sunlight


Input: Consider Input: Sentence1: Gene flow occurs when individuals move into or out of a population. 
Sentence2: when individuals move into or out of a population, it's random.


Output: individuals