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: waxy leaves are used for storing water by some plants. 
Sentence2: waxy leaves are used for water conservation by some plants.

Output: leaves


Input: Consider Input: Sentence1: an animal requires air for survival. 
Sentence2: The Moon has no atmosphere and no air.

Output: air


Input: Consider Input: Sentence1: disease has a negative impact on an organism. 
Sentence2: Bacteria and Viruses Bacteria and viruses can cause diseases.


Output: disease