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)

// -*- coding:utf-8-unix -*-

use proconio::input;
use std::str::FromStr;

#[derive(Debug)]
enum Contest {
    ABC,
    ARC,
}

impl Contest {
    fn next(&self) -> Contest {
        match self {
            Contest::ABC => Contest::ARC,
            Contest::ARC => Contest::ABC,
        }
    }
}

impl FromStr for Contest {
    type Err = ();
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s {
            "ABC" => Ok(Contest::ABC),
            "ARC" => Ok(Contest::ARC),
            _ => Err(())
        }
    }
}

fn main() {
    input! {
        mut s: String,
    }
    let s = Contest::from_str(&s).unwrap();
    println!("{:?}", s.next());
}