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 flower 's purpose is to produce seeds. 
Sentence2: Every job has meaning and purpose.

Ex Output:
purpose


Ex Input:
Sentence1: Telephone Telephone calls are expensive. 
Sentence2: Communicating by transmitting sound is expensive.

Ex Output:
expensive


Ex Input:
Sentence1: Wings are part of the exoskeleton and attached to the thorax. 
Sentence2: wings are attached to insects' thorax.

Ex Output:

Wings