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: All oaks are trees. 
Sentence2: Cutting down oaks has a negative impact on an ecosystem.

Output: oaks


Input: Consider Input: Sentence1: Oil and gasoline are fossil fuels. 
Sentence2: lawn mowers convert fossil fuels into motion.

Output: fossil


Input: Consider Input: Sentence1: decomposition increases amount of organic matter in soil. 
Sentence2: Dissolved oxygen increases the amount of organic matter in soil.


Output: amount