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: Visible and invisible light is energy in the form of electromagnetic waves. 
Sentence2: Eyes are used for seeing animals by sensing electromagnetic waves.

Ex Output:
electromagnetic


Ex Input:
Sentence1: a light bulb is used for seeing in the dark. 
Sentence2: light is required for seeing.

Ex Output:
seeing


Ex Input:
Sentence1: Nonmetals are the 17 elements in the upper right hand corner of the periodic table. 
Sentence2: The periodic table has far fewer of the elements listed in the right hand corner.

Ex Output:

corner