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: Interestingly, a squid is also a mollusk. 
Sentence2: squids have a circulatory system with one or two hearts that pump blood.

Ex Output:
squid


Ex Input:
Sentence1: Weather Clear weather usually means good visibility. 
Sentence2: High pressure systems can cause good visibility.

Ex Output:
good


Ex Input:
Sentence1: Vertebrates generally have a backbone called the spinal column. 
Sentence2: Vertebrates are animals that have a spinal column in their skeletal system.

Ex Output:

column