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.

Ex Input:
Sentence1: skin is used for protecting the body from harmful substances. 
Sentence2: Acids are harmful to tissue.

Ex Output:
harmful


Ex Input:
Sentence1: a solution is formed by one substance being dissolved in another substance. 
Sentence2: A solution is formed when limestone is dissolved in ocean water.

Ex Output:
formed


Ex Input:
Sentence1: creating paper requires cutting down trees. 
Sentence2: To cut down a tree is like destroying a life.

Ex Output:

cutting