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: a sifter is used for separating mixtures. 
Sentence2: a sifter is used for some recipes.

Output: sifter


Input: Consider Input: Sentence1: All sharks are predators. 
Sentence2: hiding can be used for avoiding sharks.

Output: sharks


Input: Consider Input: Sentence1: Biomes are simply environments that have some things in common. 
Sentence2: Wetlands are extremely important environments.


Output: environments