Problem:
Score : 100 points

Problem Statement

Two deer, AtCoDeer and TopCoDeer, are playing a game called Honest or Dishonest.
In this game, an honest player always tells the truth, and an dishonest player always tell lies.
You are given two characters a and b as the input. Each of them is either H or D, and carries the following information:

If a=H, AtCoDeer is honest; if a=D, AtCoDeer is dishonest.
If b=H, AtCoDeer is saying that TopCoDeer is honest; if b=D, AtCoDeer is saying that TopCoDeer is dishonest.

Given this information, determine whether TopCoDeer is honest.

Constraints

a=H or a=D.

b=H or b=D.

Input

The input is given from Standard Input in the following format:

a b

Output

If TopCoDeer is honest, print H. If he is dishonest, print D.

Sample Input 1

H H

Sample Output 1

H

In this input, AtCoDeer is honest. Hence, as he says, TopCoDeer is honest.

Sample Input 2

D H

Sample Output 2

D

In this input, AtCoDeer is dishonest. Hence, contrary to what he says, TopCoDeer is dishonest.

Sample Input 3

D D

Sample Output 3

H

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace A
{
    class Program
    {
        public static void Main(string[] args)
        {
            var n = ReadLineStringSplit();
            var result = "";

            //Atcoderくんが正直の場合
            if(n[0] == "H") {
                result = n[1];
            }
            //Atcoderくんが嘘つきの場合
            else if(n[0] == "D") {
                result = (n[1] == "H") ? "D": "H";
            }

            Console.WriteLine(result);
            ReadLine();
        }

        /// <summary>
        /// コンビネーション
        /// </summary>
        /// <param name="n"></param>
        /// <param name="m"></param>
        /// <returns></returns>
        static int nCm(int n, int m)
        {
            if (m == 0) return 1;
            if (n == 0) return 0;
            return n * nCm(n - 1, m - 1) / m;
        }

        /// <summary>
        /// stringを一文字ずつintにキャストして配列に変換します。
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public static int[] StringCharArrayIntArray(string str)
        {
            List<int> b = new List<int>();
            for (int i = 0; i < str.Length; i++) {
                b.Add( int.Parse(str[i].ToString()));
            }
            return b.ToArray();
        }

        public static string ReadLine()
        {
            return Console.ReadLine();
        }

        public static int ReadLineInt()
        {
            return int.Parse(Console.ReadLine());
        }

        public static string[] ReadLineStringSplit(char a = ' ')
        {
            return ReadLine().Split(a).ToArray();
        }

        public static int[] ReadLineIntSpilit(char a = ' ')
        {
            return ReadLine().Split(a).Select(x => int.Parse(x)).ToArray();
        }

        static string[] GetAplhaLowerArray() => new string[]{ "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"};
        static string[] GetAplhaUpperArray() => new string[] { "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z" };
    }
}