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;
			fourDigits = fourDigits / 10;
			
			sum += fourDigits % 10;
			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 a four digit number.");
		}

		
			
	}

}