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: Fertilization occurs naturally in the fallopian tubes. 
Sentence2: fertilization is used for reproduction.

Output: Fertilization


Input: Consider Input: Sentence1: And light broken into many pieces is a rainbow. 
Sentence2: Sunlight and rain can cause light to be broken into many pieces.


Output: broken