import java.util.Scanner;
//=================================================================================================
public class IfElse {
//-------------------------------------------------------------------------------------------------
    private static final Scanner keyboard = new Scanner(System.in);
//-------------------------------------------------------------------------------------------------
    public static void main(String[] args) {

        double area;
        long numberOfPeople;
        double populationDensity;

        System.out.print("What is the land area, and how many people live there? : ");
        area = keyboard.nextDouble();
        numberOfPeople = keyboard.nextLong();

        if (area > 0 && numberOfPeople >= 0) {
            populationDensity = numberOfPeople / area;
            System.out.println("That's a population density of " + populationDensity +
" per square mile");
        } else {
            System.out.println("ERROR: Invalid input");
        }

    }
//-------------------------------------------------------------------------------------------------
}
//=================================================================================================