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: friction is used for stopping a vehicle by brakes. 
Sentence2: friction is used for stopping a car by brakes.

Ex Output:
brakes


Ex Input:
Sentence1: conserving water can be used for survival in a dry environment. 
Sentence2: conserving water can be used for survival in deserts.

Ex Output:
conserving


Ex Input:
Sentence1: Ejaculation occurs when muscle contractions propel sperm from the epididymes. 
Sentence2: Ejaculation occurs when muscle contractions propel male gametes.

Ex Output:

Ejaculation