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: Antibiotics and vaccines are being stockpiled as Britain gears up to meet the bioterrorism threat. 
Sentence2: Antibiotics and vaccines are being stockpiled against another potential threat in the environment.

Output: Antibiotics


Input: Consider Input: Sentence1: plant requires seed dispersal for reproduction. 
Sentence2: plants are pollinated by birds.

Output: plant


Input: Consider Input: Sentence1: With so many does and so few older bucks, there is little competition for mating. 
Sentence2: bucks display less aggression when there are fewer older bucks.


Output: bucks