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.

Input: Consider Input: Sentence1: cell division often causes growth. 
Sentence2: Cell division leads to reproduction.

Output: cell


Input: Consider Input: Sentence1: Most pituitary hormones control other endocrine glands. 
Sentence2: Hormones tell the ovaries to produce eggs.

Output: hormones


Input: Consider Input: Sentence1: Female monotremes lack a uterus and vagina. 
Sentence2: Platypus and echidna lack a uterus and vagina.


Output: lack