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

Ex Output:
seeing


Ex Input:
Sentence1: Damage is intensified by moisture stress during drought. 
Sentence2: low amounts of rainfall intensify damage during drought.

Ex Output:
Damage


Ex Input:
Sentence1: a thermometer is used to measure temperature. 
Sentence2: When the temperature rises, the mercury expands and rises in the thermometer tube.

Ex Output:

thermometer