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: sharpening an object causes that object to change shape. 
Sentence2: sharpening a knife causes it to change shape.

Output: causes


Input: Consider Input: Sentence1: Some trees are maples. 
Sentence2: planting maples has a positive impact on an ecosystem.

Output: maples


Input: Consider Input: Sentence1: Largest of the oceans on Earth is the Pacific Ocean . 
Sentence2: The Pacific has marine biomes.


Output: Pacific