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: After a seed is planted it is watered. 
Sentence2: seeds need water.

Ex Output:
seed


Ex Input:
Sentence1: Skin color is another polygenic trait. 
Sentence2: Skin color is influenced by multiple genes.

Ex Output:
Skin


Ex Input:
Sentence1: Ethologists are scientists who study animals in their natural habitats. 
Sentence2: There are scientists who study how animals behave in their natural environment.

Ex Output:

scientists