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: Limestone caves displaying stalactites. 
Sentence2: Limestone caves are formed by depositions.

Ex Output:
Limestone


Ex Input:
Sentence1: dew is formed when water vapor condenses over night. 
Sentence2: Condensing is a gas turning into a liquid.

Ex Output:
condenses


Ex Input:
Sentence1: Heat and temperature are the same. 
Sentence2: a thermometer is used to measure heat.

Ex Output:

Heat