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: creating paper requires cutting down trees. 
Sentence2: Rainforests are destroyed by logging and all of the trees are cut down.

Ex Output:
cutting


Ex Input:
Sentence1: the ovaries are used in reproduction. 
Sentence2: Unlike most female animals, which have two functioning ovaries, the chicken usually has only one.

Ex Output:
ovaries


Ex Input:
Sentence1: being exposed to wind can cause erosion of soil. 
Sentence2: Wind erosion is slowed by wind barriers such as trees and shrubs.

Ex Output:

wind