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: Protozoa make humans sick when they become human parasites. 
Sentence2: paramecium are single celled animals that make humans sick when they become human parasites.

Output: become


Input: Consider Input: Sentence1: Genetics is the study and application of principles of inheritance to plants and animals . 
Sentence2: Pedigrees are useful tools for studying Genetics.

Output: Genetics


Input: Consider Input: Sentence1: condensing causes a liquid to form. 
Sentence2: Water is liquid and formless.


Output: liquid