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.

Ex Input:
Sentence1: Cultivation is easier if soil is loose. 
Sentence2: soil with more oxygen is easier to cultivate.

Ex Output:
Cultivation


Ex Input:
Sentence1: Capillaries are microscopic vessels. 
Sentence2: Lymph is a fluid that leaks out of microscopic vessels into spaces between cells.

Ex Output:
microscopic


Ex Input:
Sentence1: threatening behavior by predators causes a porcupine to extend its quills. 
Sentence2: porcupine can use its quills as a defense mechanism.

Ex Output:

quills