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: threatening behavior by predators causes a porcupine to extend its quills. 
Sentence2: Fishers are predators that can eat porcupines.

Ex Output:
predators


Ex Input:
Sentence1: soil is formed by weathering. 
Sentence2: Something described as loamy is formed by weathering.

Ex Output:
formed


Ex Input:
Sentence1: nerves can be used to feel heat and pressure on the skin. 
Sentence2: nerves can be used to feel heat and pressure on the epidermal layer.

Ex Output:

feel