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: bacteria can cause people to become ill. 
Sentence2: bacteria can cause people to die.

Output: bacteria


Input: Consider Input: Sentence1: Flatworms Flatworms or Platyhelminthes include flukes, tapeworms, and turbellarians. 
Sentence2: Tapeworms belong to the phylum Platyhelminthes.

Output: tapeworms


Input: Consider Input: Sentence1: Frogs are classified as amphibians. 
Sentence2: Frogs are tetrapods.


Output: Frogs