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: Energy enters ecosystems in the form of sunlight or chemical compounds. 
Sentence2: Energy enters ecosystems in the form of photons.

Ex Output:
Energy


Ex Input:
Sentence1: Insect wings are attached to the dorsal side of their thorax. 
Sentence2: wings are attached to the dorsal side of the insect.

Ex Output:
dorsal


Ex Input:
Sentence1: a generator converts kinetic energy into electrical energy. 
Sentence2: A generator converts kinetic energy into kWh.

Ex Output:

converts