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: 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: With a spatula, fold in flour mixture. 
Sentence2: a sifter is used for separating flour.

Ex Output:
flour


Ex Input:
Sentence1: if food is not immediately used by the body for energy then that food will be stored for future use. 
Sentence2: if food is not immediately used by the body for energy then it becomes fat.

Ex Output:

body