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: Refrigerators are major users of electricity. 
Sentence2: Keeping food fresh for a long period of time requires a lot of electricity.

Ex Output:
electricity


Ex Input:
Sentence1: folding an object causes that object to change shape. 
Sentence2: Folding an object causes that object to transform.

Ex Output:
causes


Ex Input:
Sentence1: Plants release oxygen during the day but not during the night. 
Sentence2: Many plants alter their position when they go to sleep at night.

Ex Output:

night