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: the force of water against the seed coat causes a root to emerge from a seed. 
Sentence2: Germination depends on the seed coat.

Ex Output:
coat


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: absorbing sunlight causes objects to heat. 
Sentence2: Absorbing sunlight causes cool objects to warm up.

Ex Output:

absorbing