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: pathogens can cause disease. 
Sentence2: pathogens affects the immune system.

Ex Output:
pathogens


Ex Input:
Sentence1: Coral reefs are made up of the accumulated exoskeletons of the coral polyp. 
Sentence2: coral polyps form reefs.

Ex Output:
polyp


Ex Input:
Sentence1: To keep cut flowers lasting longer, use a commercial florist preservative such as Floralife. 
Sentence2: Dehydrating food is used to make it last longer.

Ex Output:

lasting