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: Acids dissolve in base and turn blue litmus red. 
Sentence2: acid changes color.

Ex Output:
Acids


Ex Input:
Sentence1: rain causes erosion. 
Sentence2: Soil Erosion Soil erosion is what happens when soil is washed or blown away.

Ex Output:
erosion


Ex Input:
Sentence1: Shivering heats the body. 
Sentence2: many muscles contracting a little bit all at once heats the body.

Ex Output:

body