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 circle graph can be used to display percents. 
Sentence2: pie charts are circle graphs.

Output: circle


Input: Consider Input: Sentence1: Propane can be either a liquid or a gas. 
Sentence2: heat can be added to propane to change it's properties through the boiling process.

Output: Propane


Input: Consider Input: Sentence1: Protozoa Toxoplasma gondii Muscles Nematode Trichinella spiralis Protozoa Sarcocystis sp. 
Sentence2: Species of Sarcocystis can parasitize humans and make them sick.


Output: Sarcocystis