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: a mutation in the sex cells of a parent can cause a new trait to appear in the parent 's offspring. 
Sentence2: cancer of a parent's cells can cause a new trait to appear in their offspring.

Ex Output:
appear


Ex Input:
Sentence1: Here, the lungs supply the blood with oxygen. 
Sentence2: Brain cells die quickly if their blood supply is cut off.

Ex Output:
blood


Ex Input:
Sentence1: an earthquake causes the ground to shake. 
Sentence2: earthquakes can damage buildings.

Ex Output:

earthquake