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: Coral reefs provide food and shelter to many ocean organisms. 
Sentence2: Coral Reefs Coral reefs are threatened.

Ex Output:
Coral


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: Autotrophs absorb sunlight energy and transfer inorganic mineral nutrients into organic molecules. 
Sentence2: Producers make sunlight energy into food.

Ex Output:

Autotrophs