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: Every photograph is produced by a camera. 
Sentence2: Photographers record images.

Ex Output:
photograph


Ex Input:
Sentence1: Fission is a type of reproduction, but a baby is the result of sexual reproduction. 
Sentence2: the fallopian tubes are used to make babies.

Ex Output:
baby


Ex Input:
Sentence1: A photon is a packet of light energy. 
Sentence2: a bulb converts electrical energy into photons.

Ex Output:

photon