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: Plants use unsaturated fatty acids to store energy. 
Sentence2: Plants and fish contain fatty acids.

Ex Output:
Plants


Ex Input:
Sentence1: Herbs are medicines and aids. 
Sentence2: herbs are used for curing people when they are sick.

Ex Output:
Herbs


Ex Input:
Sentence1: an animal requires stamina to succeed at physical activities. 
Sentence2: males have more stamina.

Ex Output:

stamina