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: the ovaries are used in reproduction. 
Sentence2: Egg released by the ovary.

Output: ovaries


Input: Consider Input: Sentence1: Viruses are usually considered to be nonliving. 
Sentence2: Viruses are usually acquired from contact with infected animals.

Output: Viruses


Input: Consider Input: Sentence1: Cartilage is a tough tissue that contains a protein called collagen. 
Sentence2: Sharks have as skeleton that contains a protein called collagen.


Output: called