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.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Security.Cryptography.X509Certificates;
using System.Text.RegularExpressions;
using System.Threading;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            string S = Console.ReadLine();
          switch(S)
            {
                case "ABC":
                    Console.WriteLine("ARC");
                    break;
                case "ARC":
                    Console.WriteLine("ABC");
                    break;
            }
        }
    }
}

//文字列の入力
//string s = Console.ReadLine();
//整数の入力
//long n = long.Parse(Console.ReadLine());
//文字列配列の入力
//string[] inputStrArray = Console.ReadLine().Split(' ');
//整数配列の入力
//long[] inputLongArray = Console.ReadLine().Split(' ').Select(i => long.Parse(i)).ToArray();

//Console.WriteLine();
//Console.ReadKey();