import java.util.Scanner;

public class InputValidation {

	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		
		System.out.print("Enter a four digit number: ");
		int fourDigits = input.nextInt();
		
		System.out.println("You entered " + fourDigits);
		
		if(fourDigits < 0) {
			fourDigits = fourDigits * -1;
		}
		
		if(fourDigits >= 1000 && fourDigits < 10000) {
			int sum = fourDigits % 10;  //add the right-most digit
			fourDigits = fourDigits / 10; //get the first three digits
			
			sum = sum + (fourDigits % 10); //add the next digit
			fourDigits /= 10;
			
			sum += fourDigits % 10;
			fourDigits /= 10;
			
			sum += fourDigits % 10;
			
			System.out.println("The sum of the digits is " + sum);
			
		}
		else {
			System.out.println(fourDigits + " is not four digits.");
		}
	}

}