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: moss causes chemical weathering. 
Sentence2: If the moss was completely dried then it is dead.

Ex Output:
moss


Ex Input:
Sentence1: Leeches are external parasites. 
Sentence2: Leeches live on the surface of their hosts.

Ex Output:
Leeches


Ex Input:
Sentence1: Electron microscopes allow scientists to magnify objects hundreds of thousands of times. 
Sentence2: magnifying objects hundreds of thousands of times is used for seeing very small objects by making them appear bigger.

Ex Output:

hundreds