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: Fertilization is the penetration of the egg by a sperm. 
Sentence2: Sperm must swim from the male to the female egg.

Output: egg


Input: Consider Input: Sentence1: a solution is formed by one substance being dissolved in another substance. 
Sentence2: A solution is formed when limestone is dissolved in ocean water.

Output: formed


Input: Consider Input: Sentence1: decomposition increases amount of organic matter in soil. 
Sentence2: Plant respiration and decomposition of dead plant life consume dissolved oxygen in the water.


Output: decomposition