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: Viruses are usually considered to be nonliving. 
Sentence2: Viruses are usually acquired from contact with infected animals.

Ex Output:
Viruses


Ex Input:
Sentence1: harming an animal species causes that animal 's population to decrease. 
Sentence2: Wild animal populations have decreased drastically, due to both hunting and loss of habitat.

Ex Output:
animal


Ex Input:
Sentence1: coal is used for generating heat by burning. 
Sentence2: Here the coal is burned to produce electricity.

Ex Output:

burning