import java.util.*;

public class Main {
  public static void main(String[] args) {
    final String ABC_STR = "ABC";
        final String ARC_STR = "ARC";
        Scanner s = new Scanner(System.in);
        final String S = s.nextLine();

        if (ABC_STR.equals(S)) {
            System.out.println(ARC_STR);
        } else {
            System.out.println(ABC_STR);
        }
  }
}
/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