// Given a non-negative integer num, repeatedly add all its digits until the result has only one digit.
// For example:
// Given num = 38, the process is like: 3 + 8 = 11, 1 + 1 = 2. Since 2 has only one digit, return it.
public class DigitsAdding {
	public static void main(String[] args) {
		// test cases
		for (int i = 0; i < 40; i++) {
			System.out.println(addDigits(i));
		}
	}

	public static int addDigits(int num) {
		return (num - 1) % 9 + 1;
	}
}