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: creating wood-free paper does not require cutting down trees. 
Sentence2: creating printed media requires cutting down trees.

Output: creating


Input: Consider Input: Sentence1: Carbon cycles quickly between organisms and the atmosphere. 
Sentence2: the atmosphere is essential to all living organisms.

Output: organisms


Input: Consider Input: Sentence1: Technology permits space travel and transportation. 
Sentence2: space travel is used for moving people.


Output: space