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: Plants use unsaturated fatty acids to store energy. 
Sentence2: Plants and fish contain fatty acids.

Ex Output:
Plants


Ex Input:
Sentence1: Bees feed on nectar and pollen. 
Sentence2: Plant reproduction often requires bees and nectar.

Ex Output:
Bees


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