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: cell division often causes growth. 
Sentence2: Cell division leads to reproduction.

Ex Output:
cell


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: decomposition increases amount of organic matter in soil. 
Sentence2: Fungi increase the amount of organic matter in soil.

Ex Output:

amount