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: Algae have varied life cycles. 
Sentence2: And fish eat algae.

Output: Algae


Input: Consider Input: Sentence1: harming an animal species has a negative impact on the population size of that species. 
Sentence2: All dogs are animals .


Output: animal