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: a flashlight converts chemical energy into light energy. 
Sentence2: PALight Flashlights are the ultimate personal LED flashlights.

Ex Output:
flashlight


Ex Input:
Sentence1: Most soil nutrients are cations. 
Sentence2: decomposition increases the amount of cations in the soil.

Ex Output:
cations


Ex Input:
Sentence1: a plants require water for survival. 
Sentence2: Plants require water to live.

Ex Output:

plants