AddDigits259.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class AddDigits259 {
    static int addDigits(int num) {
        int n = num;
        while (n >= 10) {
            n = getsum(n);
        }
        return n;
    }

    static int getsum(int n) {
        String str = String.valueOf(n);
        int sum = 0;
        for (char c : str.toCharArray()) {
            sum += (int) (c - '0');
        }
        System.out.println(sum);
        return sum;
    }

    public static void main(String[] args) throws Exception {
        FastScanner fs = new FastScanner();
        int n = fs.nextInt();
        System.out.println(addDigits(n));
    }

    //////////////////////////////////////////////////////////////////////////////////
    //////////////////////////////////////////////////////////////////////////////////

    static class FastScanner {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer("");

        String next() {
            while (!st.hasMoreTokens())
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        int[] readArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            return a;
        }

        long nextLong() {
            return Long.parseLong(next());
        }
    }
}