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: high mountains with well-rounded peaks can be formed by collision of crustal plates. 
Sentence2: high mountains with well-rounded peaks can be formed by collision of plate tectonics.

Output: collision


Input: Consider Input: Sentence1: looking at bright objects has a negative impact on the eyes. 
Sentence2: Looking at bright objects have a negative impact on the retina.

Output: bright


Input: Consider Input: Sentence1: Ozone depletion results in higher levels of UV radiation reaching Earth. 
Sentence2: UV radiation causes DNA damage and mutations 3.3.


Output: UV