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: gills are used for breathing water by aquatic animals. 
Sentence2: gills are used for breathing water by sharks.

Output: are


Input: Consider Input: Sentence1: Urine leaves the body through a sphincter in the process of urination. 
Sentence2: urine leaves the body upon relaxation of a muscle.

Output: Urine


Input: Consider Input: Sentence1: Viruses are so small that they can be seen only with an electron microscope. 
Sentence2: Viruses include the Tobacco Mosaic Virus.


Output: Viruses