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::io::prelude::*;

fn main() -> io::Result<()> {
    let mut input = String::new();
    io::stdin().read_to_string(&mut input)?;
    io::stdout().write_all(match input.as_str() {
        "ABC\n" => b"ARC\n",
        "ARC\n" => b"ABC\n",
        _ => panic!("Unknown event"),
    })?;
    Ok(())
}