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: protein is used to repair cells by the human body. 
Sentence2: Wound healing requires protein.

Output: protein


Input: Consider Input: Sentence1: Blood pH may become unbalanced if the rate of breathing is too fast or too slow. 
Sentence2: If Someone Is Hyperventilating Hyperventilation is caused by breathing too deeply, too fast.

Output: breathing


Input: Consider Input: Sentence1: seeing requires light. 
Sentence2: Seeing requires photons.


Output: seeing