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: a stopwatch is used to measure time. 
Sentence2: Time can be measured with a clock or watch.

Output: measure


Input: Consider Input: Sentence1: Mollusks live in most terrestrial, freshwater, and marine habitats. 
Sentence2: Clams live in freshwater habitats.

Output: freshwater


Input: Consider Input: Sentence1: Coral reefs provide food and shelter to many ocean organisms. 
Sentence2: Coral Reefs Coral reefs are threatened.


Output: Coral