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: Oxygen fatigue is a shortage of oxygen reaching the brain. 
Sentence2: Plants can reduce fatigue during the daytime.

Output: fatigue


Input: Consider Input: Sentence1: threatening behavior by predators causes a porcupine to extend its quills. 
Sentence2: Fishers are one of the few specialized predators on porcupines.

Output: predators


Input: Consider Input: Sentence1: being burried under soil and mud changes peat into coal through extreme heat and pressure in a swamp over a long period of time. 
Sentence2: Marble is used for sculptures, and coal is used for fuel and energy like light.


Output: coal