import java.util.*;
import java.util.function.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	
	public static void main (String[] args) throws java.lang.Exception
	{
        Recursive<Function<Integer,Integer>> sumDigits = new Recursive<>();
		sumDigits.func = (Integer number) -> {
		    int s = Arrays.asList( String.valueOf(number).split("") )
		        .stream()
                .map(Integer::valueOf)
                .mapToInt(i->i)
                .sum();
            return s < 10 ? s : sumDigits.func.apply(s);
		};
		System.out.println(sumDigits.func.apply(100) == 1);
		System.out.println(sumDigits.func.apply(101) == 1);
		System.out.println(sumDigits.func.apply(55) == 1);
		System.out.println(sumDigits.func.apply(56) == 1);
	}
	static class Recursive<I> {
        public I func;
    }

}