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: Cells are programmed to divide only a set number of times. 
Sentence2: Cells reproduce asexually, by dividing.

Ex Output:
divide


Ex Input:
Sentence1: Some pelycosaurs gave rise to a group of animals called therapsids. 
Sentence2: Like most other groups of synapsids, all pelycosaurs are now extinct.

Ex Output:
pelycosaurs


Ex Input:
Sentence1: All photos are digital images. 
Sentence2: satellites are used to take photos from space.

Ex Output:

photos