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: Weather today is said to be sunny and clear. 
Sentence2: High pressure systems cause it to be sunny.

Ex Output:
sunny


Ex Input:
Sentence1: Male dogs use pheromones in urine to mark their territory. 
Sentence2: Pheromones are hormones that are thought to stimulate, through smell, sexual reactions in animals.

Ex Output:
pheromones


Ex Input:
Sentence1: a planet rotating causes cycles of day and night on that planet. 
Sentence2: Gravitational pull causes alternative day cycles.

Ex Output:

day