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: Protein Protein is needed for tissue maintenance and repair. 
Sentence2: protein repairs cells.

Ex Output:
Protein


Ex Input:
Sentence1: if an organism becomes too hot then that organism may die. 
Sentence2: if an organism overheats then that organism may die.

Ex Output:
die


Ex Input:
Sentence1: a cactus stem is used for storing water. 
Sentence2: A cactus stem is used to reserve moisture.

Ex Output:

cactus