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: riding a bike does not cause pollution. 
Sentence2: riding a bike does not release particles.

Output: bike


Input: Consider Input: Sentence1: Mating is generally preceded by courtship. 
Sentence2: Mating is generally similar across species.

Output: Mating


Input: Consider Input: Sentence1: Viruses cannot reproduce by themselves. 
Sentence2: Viruses Viruses are the smallest agents of disease.


Output: Viruses