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: Earth's Atmosphere Earth's atmosphere is the layer of gasses that surrounds the earth. 
Sentence2: weather refers to the conditions in the layer of gasses that surrounds the earth.

Ex Output:
earth


Ex Input:
Sentence1: Insect wings are attached to the dorsal side of their thorax. 
Sentence2: wings are attached to the dorsal side of the insect.

Ex Output:
dorsal


Ex Input:
Sentence1: a flower 's purpose is to produce seeds. 
Sentence2: a flower's purpose is to create new plants.

Ex Output:

's