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: a flashlight converts chemical energy into light energy. 
Sentence2: Only as long as there are batteries in the flashlight, the flashlight will function.

Output: flashlight


Input: Consider Input: Sentence1: Lancelet larvae are free-swimming. 
Sentence2: some larvae lack a hardened backbone.

Output: larvae


Input: Consider Input: Sentence1: Protozoa can be classified on the basis of how they move. 
Sentence2: Cryptosporidium parvum is the hardest protozoa to kill.


Output: Protozoa