For whatever reason, architects and builders have to have a number they are afraid of. In America at least, there are buildings that don't have a thirteenth floor. Less than ten percent of Manhattan condominiums have a thirteenth floor. But in South Korea, that number is four. The reason for this is because it sound very similar to the word for death. Because of this it is common for buildings to have three and a three-a floor instead of four. Have you noticed any other countries that skip numbers?