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)

extern crate proconio;
use proconio::fastout;
use proconio::marker::Chars;

#[fastout]
fn main() {
    proconio::input! {
        mut s: Chars,
    }
    {
        let g = &mut s[1];
        *g = match *g {
            'B' => 'R',
            'R' => 'B',
            _ => unreachable!(),
        };
    }
    for c in s {
        print!("{}", c);
    }
    println!("");
}