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: cell division often causes growth. 
Sentence2: Mitosis is cell division.

Ex Output:
cell


Ex Input:
Sentence1: Amphibians have permeable skin that easily absorbs substances from the environment. 
Sentence2: permeable skin easily absorbs air to breathe through.

Ex Output:
absorbs


Ex Input:
Sentence1: Water vapor in the atmosphere condenses, then falls to the earth's surface as rain and snow. 
Sentence2: Transpiration is when water vapor moves from plants and falls to the earth's surface as rain and snow.

Ex Output:

earth's