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: Some mollusks are nearly microscopic. 
Sentence2: Some squids are nearly microscopic.

Ex Output:
Some


Ex Input:
Sentence1: Centrioles come in pairs. 
Sentence2: Something that comes in pairs are organelles involved in cell division.

Ex Output:
come


Ex Input:
Sentence1: Thermal conduction removes heat from the center. 
Sentence2: when a cooler object touches a warmer object, heat is removed from the center.

Ex Output:

center