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: Muscles can only contract. 
Sentence2: Contraction is a type of movement.

Output: contract


Input: Consider Input: Sentence1: freezing means changing from a liquid into a solid by reducing heat energy. 
Sentence2: Water freezes into ice when cooled.

Output: freezing


Input: Consider Input: Sentence1: an aquatic animal requires great amounts of water to survive. 
Sentence2: Beavers are primarily aquatic animals.


Output: animal