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)

#![allow(unused)]

//
// Based on EbTech's Scanner https://stackoverflow.com/q/56449027
//
struct Scanner<'a, R: std::io::BufRead> {
    reader: R,
    buf: String,
    iter: std::str::SplitWhitespace<'a>,
}

impl<'a, R: std::io::BufRead> Scanner<'a, R> {
    fn new(reader: R) -> Self {
        Self { reader, buf: String::new(), iter: "".split_whitespace() }
    }

    fn get_str(&mut self) -> &str {
        if let Some(t) = self.iter.next() {
            return t;
        }
        self.buf.clear();
        self.reader.read_line(&mut self.buf).expect("I/O error");
        self.iter = unsafe { std::mem::transmute(self.buf.split_whitespace()) };
        self.get_str()
    }

    fn get<T: std::str::FromStr>(&mut self) -> T {
        self.get_str().parse().ok().expect("Parse error")
    }
}

fn main() {
    let stdin = std::io::stdin();
    solve(Scanner::new(stdin.lock()));
}

fn solve<R: std::io::BufRead>(mut sc: Scanner<R>) {
    let s: String = sc.get();

    if s == "ABC" {
        println!("ARC");
    } else {
        println!("ABC");
    }
}