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.

Ex Input:
Sentence1: Leaves make food for the plant. 
Sentence2: Some producers have leaves to help use energy and inorganic molecules.

Ex Output:
Leaves


Ex Input:
Sentence1: freezing means changing from a liquid into a solid by reducing heat energy. 
Sentence2: Water freezes into ice when cooled.

Ex Output:
freezing


Ex Input:
Sentence1: Cynodonts became more mammal-like as they continued to evolve. 
Sentence2: Cynodonts evolved to become more related to the primitive warm-blooded vertebrate animal.

Ex Output:

Cynodonts