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 PHP (7.4.4) (judge verdict: Accepted)

<?php
const CONTEST_A = 'ABC';
const CONTEST_B = 'ARC';
$s = trim(fgets(STDIN));
if ($s == CONTEST_A) {
    echo CONTEST_B;
} else {
    echo CONTEST_A;
}