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: Herbs are medicines and aids. 
Sentence2: herbs are used for curing people when they are sick.

Ex Output:
Herbs


Ex Input:
Sentence1: the Earth being tilted on its rotating axis causes seasons. 
Sentence2: the planet's orbit and tilt causes seasons.

Ex Output:
seasons


Ex Input:
Sentence1: wind causes erosion. 
Sentence2: Flooding is one of the results of erosion.

Ex Output:

erosion