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: Examples of gametes are ova and spermatozoa. 
Sentence2: fertilization of ova and spermatozoa produces a diploid zygote.

Output: ova


Input: Consider Input: Sentence1: If there is enough moisture in the clouds, rain is produced. 
Sentence2: Clouds lacking water reduces rainfall.

Output: clouds


Input: Consider Input: Sentence1: And somewhere a beagle howls a most pitiful sound. 
Sentence2: wolves use sound to warn other wolves.


Output: sound