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: Mutations are essential for evolution to occur. 
Sentence2: Genes are altered for evolution to occur.

Output: evolution


Input: Consider Input: Sentence1: Ground tissue makes up most of the interior of a plant. 
Sentence2: ground tissue makes up most of the interior of a dandelion.

Output: Ground


Input: Consider Input: Sentence1: An organic molecule is one involving carbon. 
Sentence2: organic molecules cycle quickly between organisms and the atmosphere.


Output: molecule