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: Runoff water is wasted water. 
Sentence2: Streams may start with wasted water.

Ex Output:
wasted


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: chemical splashing can cause harm to humans. 
Sentence2: gardening and painting supplies can cause harm to humans.

Ex Output:

cause