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: Macroevolution occurs over geologic time above the level of the species. 
Sentence2: adding new genes with special capability occurs over geologic time above the level of the species.

Ex Output:
above


Ex Input:
Sentence1: Flies are insects with two wings. 
Sentence2: Flies are arthropods with two wings.

Ex Output:
Flies


Ex Input:
Sentence1: Dilation occurs when cell walls relax. 
Sentence2: Blood vessels dilate, the flow of blood to the skin increases and the muscles relax.

Ex Output:

Dilation