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: Lymphocytes are the key cells involved in the immune response. 
Sentence2: The key cells involved in the immune response produce antibodies.

Output: cells


Input: Consider Input: Sentence1: Fully cooking oysters kills the bacteria. 
Sentence2: Fully cooking oysters can prevent illness.

Output: Fully


Input: Consider Input: Sentence1: dropping an object into water causes vibrations in the water. 
Sentence2: Lateral line systems, usually found in fish, detect vibrations in the water.


Output: vibrations