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: Introns are regions that do not code for proteins. 
Sentence2: regions that do not code for proteins are removed by RNA splicing.

Ex Output:
code


Ex Input:
Sentence1: Female monotremes lack a uterus and vagina. 
Sentence2: Babies are normally delivered from the uterus through the vagina.

Ex Output:
uterus


Ex Input:
Sentence1: All plants have a characteristic life cycle that includes alternation of generations. 
Sentence2: bamboo has  a characteristic life cycle that includes alternation of generations.

Ex Output:

alternation