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: June Summer Triangle Three bright stars light up the summer sky. 
Sentence2: Nuclear reactions in stars cause them to brighten up the summer sky.

Ex Output:
bright


Ex Input:
Sentence1: camouflage is used for protection by prey against predators. 
Sentence2: blending is used for protection.

Ex Output:
protection


Ex Input:
Sentence1: Evolution occurs by a process called natural selection. 
Sentence2: Actually, evolution is adaptation to change.

Ex Output:

Evolution