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: Lymphocytes are the key cells involved in the immune response. 
Sentence2: The key cells involved in the immune response produce antibodies.

Output: cells


Input: Consider Input: Sentence1: Roundworms make up the phylum Nematoda. 
Sentence2: Also, nematoda and rotifera are important groups contributing to soils.

Output: Nematoda


Input: Consider Input: Sentence1: when the season changes , the amount of daylight will change. 
Sentence2: when the season changes  the amount of hours will change.


Output: amount