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: a mutation in the sex cells of a parent can cause a new trait to appear in the parent 's offspring. 
Sentence2: cancer of a parent's cells can cause a new trait to appear in their offspring.

Output: appear


Input: Consider Input: Sentence1: moss causes chemical weathering. 
Sentence2: Sphagnum moss mixed with peat moss.

Output: moss


Input: Consider Input: Sentence1: If the parasite causes harm, it is a pathogen. 
Sentence2: When a parasite produces memory cells, active immunity results.


Output: parasite