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: natural magnetism is used for pointing north by a compass. 
Sentence2: For the ordinary compass, align to the North direction.

Ex Output:
north


Ex Input:
Sentence1: if humans disturb animals in a location then those animals will move to a different location. 
Sentence2: The human being is self-aware.

Ex Output:
humans


Ex Input:
Sentence1: Viruses Viruses Viruses are simple units which invade cells. 
Sentence2: Viruses are simple units which are neither prokaryotes nor eukaryotes.

Ex Output:

Viruses