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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;

public class Main {

	static BufferedReader reader;
	final static boolean MODE_DEBUG = false;
	//static field here
	final static String[] c = new String[]{"ABC","ARC"};
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		reader = new BufferedReader(new InputStreamReader(System.in));
		//code here
		String S = readLine()[0];
		if(S.equals(c[0])) {print(c[1]);}
		if(S.equals(c[1])) {print(c[0]);}
		//String[] s = readLine();
		//print(num);
	}
	
	//functions here
	//note that all methods should be STATIC


	private static <T> int arraySearch(T needle, T[] heystack) {
		for(int i=0;i<heystack.length;i++) {
			if(needle.equals(heystack[i])) {
				return i;
			}
		}
		return -1;
	}
	private static int[] sort(int[] base) {
		int[] copy = array_copy(base);
		Arrays.sort(copy);
		return copy;
	}
	private static int[] array_copy(int[] base) {
		int[] copy = new int[base.length];
		for(int i=0;i<base.length;i++) {
			copy[i] = base[i];
		}
		return copy;
	}
	private static int[] asArray(ArrayList<Integer> ints) {
		int[] intlist = new int[ints.size()];
		for(int i=0;i<intlist.length;i++) {
			intlist[i] = ints.get(i);
		}
		return intlist;
	}
	private static String[] readLine(){
		try{
			return reader.readLine().split(" ");
		}catch(Exception e){
			e.printStackTrace();
			return new String[]{e.getMessage()};
		}
	}
	private static int[] readLineInt(){
		try{
			String[] s = readLine();
			int[] ints = new int[s.length];
			for(int i=0;i<ints.length;i++) {
				ints[i] = Integer.parseInt(s[i]);
			}
			return ints;
		}catch(Exception e){
			e.printStackTrace();
			return null;
		}
	}
	private static byte[] readLineByte(){
		try{
			String[] s = readLine();
			byte[] bytes = new byte[s.length];
			for(int i=0;i<bytes.length;i++) {
				bytes[i] = Byte.parseByte(s[i]);
			}
			return bytes;
		}catch(Exception e){
			e.printStackTrace();
			return null;
		}
	}
	private static char[] readLineChar(){
		try{
			String[] s = readLine();
			char[] chars = new char[s.length];
			for(int i=0;i<chars.length;i++) {
				chars[i] = (char)Integer.parseInt(s[i]);
			}
			return chars;
		}catch(Exception e){
			e.printStackTrace();
			return null;
		}
	}
	private static void print(Object o){
		System.out.println(o);
	}
	private static void print(){
		System.out.println();
	}
	private static void printd(Object o){
		if(MODE_DEBUG)System.err.println(o);
	}
	private static void printd(){
		if(MODE_DEBUG)System.err.println();
	}
}