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 herbivores have more than one stomach. 
Sentence2: Camels are an herbivore.

Ex Output:
herbivores


Ex Input:
Sentence1: mineral graphite is used for making pencil lead. 
Sentence2: Diamond and graphite are made of carbon.

Ex Output:
graphite


Ex Input:
Sentence1: if heat is conducted to an object then that object will become hot. 
Sentence2: rocks become hot very slow.

Ex Output:

become