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: Cells are programmed to divide only a set number of times. 
Sentence2: Cells reproduce asexually, by dividing.

Output: divide


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: Cryptic coloration is a type of camouflage. 
Sentence2: Cryptic coloration is used for protection by prey against predators.


Output: Cryptic