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

    public class Program
    {
        public static void Main(string[] args)
        {
            new A().test();
        }
    }

	public class A
	{
		public void test()
		{
			// 普通の文字列
			var input = CommonRead.ReadStr();

			if(input == "ABC")
			{
				Console.WriteLine("ARC");
			}
			else
			{
				Console.WriteLine("ABC");
			}


		}
	}


static class CommonRead
{
    public static string ReadStr()
    {
        return Console.ReadLine();
    }
    public static string[] ReadStrA()
    {
        return ReadStr().Split(' ');
    }
    public static List<string> ReadStrL()
    {
        return ReadStrA().ToList();
    }
    public static int ReadInt()
    {
        return Convert.ToInt32(ReadStr());
    }
    public static int[] ReadIntA()
    {
        return ReadStrA().Select(s => Convert.ToInt32(s)).ToArray();
    }
    public static List<int> ReadIntL()
    {
        return ReadStrA().Select(s => Convert.ToInt32(s)).ToList();
    }
    public static long ReadLong()
    {
        return Convert.ToInt64(ReadStr());
    }
    public static long[] ReadLongA()
    {
        return ReadStrA().Select(s => Convert.ToInt64(s)).ToArray();
    }
    public static List<long> ReadLongL()
    {
        return ReadStrA().Select(s => Convert.ToInt64(s)).ToList();
    }

    public static decimal ReadDecimal()
    {
        return Convert.ToDecimal(ReadStr());
    }
    public static decimal[] ReadDecimalA()
    {
        return ReadStrA().Select(s => Convert.ToDecimal(s)).ToArray();
    }
    public static List<decimal> ReadDecimalL()
    {
        return ReadStrA().Select(s => Convert.ToDecimal(s)).ToList();
    }

    public static double ReadDouble()
    {
        return Convert.ToDouble(ReadStr());
    }
    public static double[] ReadDoubleA()
    {
        return ReadStrA().Select(s => Convert.ToDouble(s)).ToArray();
    }
    public static List<double> ReadDoubleL()
    {
        return ReadStrA().Select(s => Convert.ToDouble(s)).ToList();
    }

}