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: Moisture is required for the microorganisms to grow. 
Sentence2: Moisture can cause infections to grow.

Output: Moisture


Input: Consider Input: Sentence1: Any antigen that causes an allergy is called an allergen. 
Sentence2: molds are antigens.

Output: antigen


Input: Consider Input: Sentence1: a flashlight requires a source of electricity to produce light. 
Sentence2: Battery can be tested with flashlight.


Output: flashlight