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: killing microorganisms in food can be used to extend the shelf life of that food. 
Sentence2: Cooking can be used to extend the shelf life of food.

Output: be


Input: Consider Input: Sentence1: a warm front causes cloudy and rainy weather. 
Sentence2: Stratus clouds are associated with a warm front.

Output: front


Input: Consider Input: Sentence1: Organs of excretion make up the excretory system. 
Sentence2: Excretory system is composed of a dorsal excretory gland and a pair of Malpighian tubules.


Output: excretory