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: Fractures heal when osteoclasts form new bone. 
Sentence2: Fractures A fracture is a broken or cracked bone.

Ex Output:
Fractures


Ex Input:
Sentence1: Urine leaves the body through a sphincter in the process of urination. 
Sentence2: urine leaves the body upon relaxation of a muscle.

Ex Output:
Urine


Ex Input:
Sentence1: Friendship usually precedes courtship, and courtship, marriage. 
Sentence2: Friendship often comes before mating.

Ex Output:

Friendship