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: if fossils of a water animal or plant are found in a place then that place used to be covered by water in the past. 
Sentence2: if remains of prehistoric life are found in a place then that place used to be covered by water.

Output: be


Input: Consider Input: Sentence1: if an animal lives under ground then that animal will be protected from a wild fire. 
Sentence2: animals that live under ground in California will be protected from some natural disasters.

Output: animal


Input: Consider Input: Sentence1: DNA DNA is deoxyribonucleic acid. 
Sentence2: Oncogenes promote the division of cells with damaged deoxyribonucleic acid.


Output: acid