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-csc 3.5.0) (judge verdict: Accepted)

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

    namespace cysharp_test
    {
        class Program
        {
            static void Main (string[] args)
            {
                new Program ().solve ();
            }

            void solve ()
            {
            var s = Console.ReadLine();
            Console.WriteLine(s == "ARC" ? "ABC" : "ARC");
            Console.ReadKey ();
            }
        }
        struct Vector2
        {
            public Vector2 (long x, long y)
            {
                this.x = x;
                this.y = y;
            }

            public long x, y;

            public static Vector2 operator + (Vector2 a, Vector2 b)
            {
                return new Vector2 (a.x + b.x, a.y + b.y);
            }

            public static Vector2 operator - (Vector2 a, Vector2 b)
            {
                return new Vector2 (a.x - b.x, a.y - b.y);
            }

            public static Vector2 operator * (Vector2 a, long scala)
            {
                return new Vector2 (a.x * scala, a.y + scala);
            }

            public static bool operator == (Vector2 a, Vector2 b)
            {
                return (a.x == b.x) && (a.y == b.y);
            }

            public static bool operator != (Vector2 a, Vector2 b)
            {
                return !(a.x == b.x) && (a.y == b.y);
            }

            public override int GetHashCode ()
            {
                return (int) (x + y);
            }

            public override bool Equals (object obj)
            {
                if (!(obj == null) && obj is Vector2)
                {
                    return (this == (Vector2) obj);
                }
                else return false;
            }

            public override string ToString ()
            {
                return ("(" + x + "," + y + ")");
            }
        }
    }