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: Speciation events are thus examples of macroevolution. 
Sentence2: Speciation events occur over geologic time above the level of the species.

Ex Output:
Speciation


Ex Input:
Sentence1: Mating is generally preceded by courtship. 
Sentence2: Mating is generally similar across species.

Ex Output:
Mating


Ex Input:
Sentence1: when the season changes , the amount of daylight will change. 
Sentence2: Changing the angle of the sun will change the amount of daylight.

Ex Output:

amount