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# (Mono-mcs 6.8.0.105) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.IO.Pipes;
using System.Runtime;
 
namespace Csharponly
{
    class Program
    {
        static public void Main()
        {
		string S = Onestring();
        string ans = "ABC";
        if(S == "ABC"){
            ans = "ARC";
        }
		Console.WriteLine(ans);
	
        }
 
　　　　//一つの文字列を受け渡す
        static string Onestring()
        {
            return Console.ReadLine();
        }
 
        //複数の文字列を配列で受け渡す
        //文字列と文字列の間は" "で区切る
        static string[] Arraystring()
        {
            return Console.ReadLine().Split(' ');
        }
 
        //一つの数字を受け渡す
        static int Oneint()
        {
            return int.Parse(Console.ReadLine());
        }
 
        //複数の数字を配列で受け渡す
        //数字と数字の間は" "で区切る
        static int[] Arrayint()
        {
            String[] input_line = Console.ReadLine().Split(' ');
            int[] input_num = new int[input_line.Length];
            for (int i = 0; i < input_line.Length; i++)
            {
                input_num[i] = int.Parse(input_line[i]);
            }
            return input_num;
        }
    }
}