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: Bound and free ribosomes are structurally identical and interchangeable. 
Sentence2: Bound and free structures are in the cytoplasm where proteins are made.

Output: Bound


Input: Consider Input: Sentence1: Mitosis is cell division. 
Sentence2: Chromosomes are the form of the genetic material of a cell during mitosis.

Output: Mitosis


Input: Consider Input: Sentence1: Killer whales prefer shallow and colder coastal waters. 
Sentence2: Killer whales are a marine species.


Output: Killer