import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();
		int D = scan.nextInt();
		scan.close();
		if(N == D) {
			StringBuilder sb = new StringBuilder();
			for(int i = 0; i < N; i++) {
				sb.append("A");
			}
			System.out.println(sb.toString());
		}else if(N > D){
			int k = N - D;
			StringBuilder sb = new StringBuilder();
			for(int i = 0; i < D; i++) {
				sb.append("A");
			}
			for(int i = 0; i < k; i++) {
				sb.append("C");
			}
			System.out.println(sb.toString());
		}else {
			int k1 = D - N;
			int k2 = 2 * N - D;
			StringBuilder sb = new StringBuilder();
			for(int i = 0; i < k2; i++) {
				sb.append("A");
			}
			for(int i = 0; i < k1; i++) {
				sb.append("B");
			}
			System.out.println(sb.toString());
		}
	}
}