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: Any antigen that causes an allergy is called an allergen. 
Sentence2: molds are antigens.

Output: antigen


Input: Consider Input: Sentence1: if an organism becomes too hot then that organism may die. 
Sentence2: a plant can collapse if it gets too hot.

Output: hot


Input: Consider Input: Sentence1: Chemical weathering is strongest in tropical environments. 
Sentence2: moss is the strongest in tropical enviornments.


Output: environments