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.

Input: Consider Input: Sentence1: the mass of a planet causes the pull of gravity on that planet. 
Sentence2: the mass of a planet is what causes things to have weight.

Output: mass


Input: Consider Input: Sentence1: Without light there is no sense of vision. 
Sentence2: Glass causes a sense of vision.

Output: sense


Input: Consider Input: Sentence1: Polyps usually reproduce asexually. 
Sentence2: benign growths in the colon reproduce asexually.


Output: asexually