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: Heterotrophs are living things that cannot make their own food. 
Sentence2: food contains organic molecules.

Output: food


Input: Consider Input: Sentence1: a greenhouse is used to protect plants by keeping them warm. 
Sentence2: Flower size varies by plant.

Output: plants


Input: Consider Input: Sentence1: Metal or aluminum trees are conductors of electricity. 
Sentence2: wiring requires metal or aluminum for electricity.


Output: Metal