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: Distance is measured in meters the SI unit of distance. 
Sentence2: The SI unit of distance is in meters.

Ex Output:
SI


Ex Input:
Sentence1: Plants exhibit phototropism, or growing toward a light source. 
Sentence2: Bamboos are vigorous, rugged plants.

Ex Output:
Plants


Ex Input:
Sentence1: a solution is formed by one substance being dissolved in another substance. 
Sentence2: Solvents are substances, usually liquid, that dissolve other substances.

Ex Output:

substance