let floorsInTheHouse = 9;
const numberOfApartmentsPerFloor = 4;
let apartmentNumber = +prompt('Укажите номер квартиры');

let entranceNumber = Math.ceil(apartmentNumber / (floorsInTheHouse * numberOfApartmentsPerFloor));
let floorNumber = Math.ceil((apartmentNumber % (floorsInTheHouse * numberOfApartmentsPerFloor)) / numberOfApartmentsPerFloor);

alert(`Номер подезда - ${entranceNumber}, этаж = ${(floorNumber === 0) ? (floorNumber = floorsInTheHouse) : floorNumber}`);