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: Stress is the applied force, strain is the change in shape. 
Sentence2: Paper is crumbled when stress and strain is applied in order to change the shape.

Output: Stress


Input: Consider Input: Sentence1: if soil is permeable then water easily flows through that soil. 
Sentence2: The increase in permeability is caused by the formation and expansion of ice in the soil.

Output: permeable


Input: Consider Input: Sentence1: Amphibians have permeable skin that easily absorbs substances from the environment. 
Sentence2: Amphibians have permeable skin that can easily absorb toxins from bacterias, plants or animals.


Output: Amphibians