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

Ex Output:
Fish


Ex Input:
Sentence1: if an object is made of a material then that object has the properties of that material. 
Sentence2: items properties are the same as the materials the item is made of.

Ex Output:
made


Ex Input:
Sentence1: Air pollution harms the respiratory and circulatory systems. 
Sentence2: Nitrogen oxides harms the respiratory and circulatory systems.

Ex Output:

circulatory