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: air pollution can cause the pH of soil to decrease. 
Sentence2: Acidity is measured with a pH meter or with pH paper strips.

Output: pH


Input: Consider Input: Sentence1: dew is formed when water vapor condenses over night. 
Sentence2: dew is formed when cooling  over night.

Output: dew


Input: Consider Input: Sentence1: All echinoderms are deuterostomes . 
Sentence2: deuterostomes use pheromones to communicate with each other.


Output: deuterostomes