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 Rust (1.15.1) (judge verdict: Accepted)

use std::env;
use std::io::*;
use std::str::*;

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let s = stdin.bytes().map(|c| c.unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect::<String>();
    s.parse::<T>().ok().unwrap()
}

fn main() {
    // main の引数
    /*
        引数なしのときargs.len() = 1;
    */
    let args: Vec<String> = env::args().collect();

    let a = read::<String>();
    let A: Vec<char> = a.chars().collect();
    let b = read::<String>();
    let B: Vec<char> = b.chars().collect();

    if A[0] == B[0] {
        println!("H");
    }else {
        println!("D");
    }
}

/*
AtCoder AtCoDeer
H H 1
H D 0
D H 0
D D 1
*/