import java.util.Scanner;

/**
 * @author hellb
 *
 */
public class Main {

	private static String ARC = "ARC";

	private static String ABC = "ABC";

	/**
	 * @param args
	 */
	public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);
        String sNum1 = scan.next();
        String sResult;
        scan.close();

        if (ARC.equals(sNum1)) {
        	sResult = ABC;
        } else {
        	sResult = ARC;
        }
        System.out.print(sResult);
	}
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz