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 C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using System.Text.RegularExpressions;

class Program
{
    static int[] ReadInts()
        => Console.ReadLine()
            .Split(new[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries)
            .Select(s => int.Parse(s))
            .ToArray();

    static void Main(string[] args)
    {
        var s = Console.ReadLine();
        if (s == "ABC")
        {
            Console.WriteLine("ARC");
        }
        else
        {
            Console.WriteLine("ABC");
        }
    }
}