import java.util.Scanner;

public class Main{

	public static void main(String[] args){

		Scanner scan01 = new Scanner(System.in);
		String str = scan01.next();

		String abc = "ABC";
		String arc = "ARC";

		if(str.equals(abc)){
			System.out.println("ARC");
		}else if(str.equals(arc)){
			System.out.println("ABC");
		}
			scan01.close();
	}
}
/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