import java.util.*;

public class Main {
 	public static void main (String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int d = sc.nextInt();
		StringBuilder sb = new StringBuilder();
		if (d > n) {
		    for (int i = 0; i < n; i++) {
		        if (i < n - (d - n)) {
		            sb.append("A");
		        } else {
		            sb.append("B");
		        }
		    }
		} else {
		    for (int i = 0; i < n; i++) {
		        if (i < d) {
		            sb.append("A");
		        } else {
		            sb.append("C");
		        }
		    }
		}
		System.out.println(sb);
	}
}