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: riding a bike does not cause pollution. 
Sentence2: riding a bike does not release particles.

Ex Output:
bike


Ex Input:
Sentence1: wind is used for producing electricity. 
Sentence2: Wind is caused because of pressure differences in the atmosphere.

Ex Output:
wind


Ex Input:
Sentence1: sedimentary rocks are formed by deposition. 
Sentence2: Limestone is formed by deposition.

Ex Output:

are