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: For instance, glucose is a sugar. 
Sentence2: insulin helps cells take up sugar from the blood.

Ex Output:
sugar


Ex Input:
Sentence1: Light is the visible form of electromagnetic energy. 
Sentence2: Electromagnetic energy enters the eye through an opening called the pupil.

Ex Output:
electromagnetic


Ex Input:
Sentence1: Incandescent light bulbs use a tungsten filament sealed inside a glass bulb. 
Sentence2: Tungsten filament sealed in a glass bulb is used for seeing in the dark.

Ex Output:

bulb