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: a fire requires oxygen to burn. 
Sentence2: A fire requires something with exactly eight protons to burn.

Ex Output:
burn


Ex Input:
Sentence1: With a spatula, fold in flour mixture. 
Sentence2: a sifter is used for separating flour.

Ex Output:
flour


Ex Input:
Sentence1: Climate influences plant growth, biodiversity, and adaptations of land organisms. 
Sentence2: Desert animals are adapted to the vegetation and the climate.

Ex Output:

adaptations