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.

Input: Consider Input: Sentence1: Fish are the first known true chordates. 
Sentence2: Fish are the first known animal with a backbone.

Output: Fish


Input: Consider Input: Sentence1: Animals behave in a variety of ways which enhance their chances of survival and reproduction. 
Sentence2: Animals learn to behave to increase chances of survival.

Output: behave


Input: Consider Input: Sentence1: Sporophyte possesses stoma. 
Sentence2: Flowers form on the stoma.


Output: stoma