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: Rivers, rainwater, well water and most lakes contain fresh water. 
Sentence2: canyons are formed by rainwater.

Ex Output:
rainwater


Ex Input:
Sentence1: All sharks are predators. 
Sentence2: hiding can be used for avoiding sharks.

Ex Output:
sharks


Ex Input:
Sentence1: The length of daylight varies depending on latitude and season. 
Sentence2: Seasons change because of the latitude.

Ex Output:

latitude