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: a pulley is used for lifting objects. 
Sentence2: Resistance exercises are weight-lifting exercises.

Ex Output:
lifting


Ex Input:
Sentence1: an animal requires air for survival. 
Sentence2: The Moon has no atmosphere and no air.

Ex Output:
air


Ex Input:
Sentence1: Fine particulates are tiny pieces of soot and dust that lodge deeply in the lungs. 
Sentence2: smog contains tiny pieces of soot and dust.

Ex Output:

dust