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: triceps contracting causes a person 's elbow to straighten. 
Sentence2: muscles contracting cause a person's elbow to straighten.

Output: contracting


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: waxy leaves are used for storing water by some plants. 
Sentence2: kalenchoes use their leaves to store water.


Output: storing