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: An accounting period is simply a period of time. 
Sentence2: seconds are used to measure a period.

Output: period


Input: Consider Input: Sentence1: a light bulb is used for seeing in the dark. 
Sentence2: light is required for seeing.

Output: seeing


Input: Consider Input: Sentence1: Influenza viruses are classified as orthomyxoviruses. 
Sentence2: Antibiotics have no effect on influenza.


Output: Influenza