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: Nitrogen is found in proteins, nucleic acids, and chlorophyll. 
Sentence2: Lawns eat nitrogen.

Ex Output:
Nitrogen


Ex Input:
Sentence1: Mutations may change the structure of a chromosome or just change a single nucleotide. 
Sentence2: Mutations change DNA.

Ex Output:

Mutations