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: Mollusks are invertebrates such as the common snail. 
Sentence2: snails have no backbone.

Output: snail


Input: Consider Input: Sentence1: healing requires rest. 
Sentence2: healing requires time.

Output: healing


Input: Consider Input: Sentence1: Beavers know how to cut wood and build dams. 
Sentence2: Beavers can create lakes.


Output: Beavers