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: Endocrine glands include the pituitary, thyroid, parathyroid, adrenal, pineal and thymus glands. 
Sentence2: Some pituitary hormones can control the thyroid gland.

Ex Output:
thyroid


Ex Input:
Sentence1: Autumn brings the changing of the seasons. 
Sentence2: Earth 's tilt on its rotating axis causes autumn.

Ex Output:
Autumn


Ex Input:
Sentence1: Antigens are proteins foreign to the body. 
Sentence2: antigens are proteins.

Ex Output:

proteins