Problem:
Score : 100 points

Problem Statement

AtCoder Inc. holds a contest every Saturday.

There are two types of contests called ABC and ARC, and just one of them is held at a time.

The company holds these two types of contests alternately: an ARC follows an ABC and vice versa.

Given a string S representing the type of the contest held last week, print the string representing the type of the contest held this week.

Constraints

S is ABC or ARC.

Input

Input is given from Standard Input in the following format:

S

Output

Print the string representing the type of the contest held this week.

Sample Input 1

ABC

Sample Output 1

ARC

They held an ABC last week, so they will hold an ARC this week.

Solution in Rust (1.42.0) (judge verdict: Accepted)

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

fn main() {
    let s = stdin();
    let mut s = s.lock();
    let s = &mut s;
    let text: String = read(s).unwrap();
    let text = check(text.as_str());
    println!("{}", text)
}

fn read<T: FromStr>(s: &mut StdinLock) -> Option<T> {
    let s = s.by_ref()
        .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()
}

fn check(text: &str) -> &str {
    return if text == "ABC" { "ARC" } else { "ABC" }
}