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: Polygenic inheritance Polygenic traits are controlled by an unknown number of genes. 
Sentence2: Skin color is inherited from a number of genes.

Output: genes


Input: Consider Input: Sentence1: a polar bear requires a cold environment. 
Sentence2: polar bears live where there are fewer animals.

Output: bear


Input: Consider Input: Sentence1: Strong winds increase the concentration of oxygen available to the fire. 
Sentence2: avoid winds to keep oxygen from the fire.


Output: fire