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: melting is when solids are heated above their melting point. 
Sentence2: Ice is a solid, it's cold and it's hard.

Ex Output:
solids


Ex Input:
Sentence1: Some trees are maples. 
Sentence2: planting maples has a positive impact on an ecosystem.

Ex Output:
maples


Ex Input:
Sentence1: intense heat has a negative impact on an organism. 
Sentence2: Summer heat in the desert is intense and oppressive.

Ex Output:

heat