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: weathering means breaking down rocks from larger whole into smaller pieces by weather. 
Sentence2: Trash collectors work in all types of weather, including rain and snow.

Ex Output:
weather


Ex Input:
Sentence1: a circle graph can be used to display percents. 
Sentence2: pie charts are circle graphs.

Ex Output:
circle


Ex Input:
Sentence1: absorbing energy causes objects to heat. 
Sentence2: Energy enters an ecosystem as sunlight.

Ex Output:

energy