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: when a gas in an open container evaporates , that gas spreads out into the air. 
Sentence2: If you place gas in an open box it will evaporate and spread out into the air.

Ex Output:
gas


Ex Input:
Sentence1: Insects have 2 antennae. 
Sentence2: Insects have 2 appendages to detect sound.

Ex Output:
2


Ex Input:
Sentence1: Hydrogen bonds cause water to expand when it freezes. 
Sentence2: Water makes strong hydrogen bonds.

Ex Output:

Hydrogen