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: Humans have collected and grown mushrooms for food for thousands of years. 
Sentence2: humans have collected and grown porcinis for thousands of years.

Ex Output:
Humans


Ex Input:
Sentence1: Electrical currents cause magnetic fields. 
Sentence2: Electrical currents can cause objects to repel each other.

Ex Output:
Electrical


Ex Input:
Sentence1: irradiating food can be used to kill existing microorganisms in the food. 
Sentence2: Irradiated food improves food safety.

Ex Output:

food