import java.util.*;

public class Main {
	public static void main (String[] args) {
    	Scanner sc = new Scanner(System.in);
    	int n = sc.nextInt();
    	int d = sc.nextInt();
    	char[] ans = new char[n];
    	for (int i = n; i > 0; i--) {
    	    if (i < d) {
    	        ans[i - 1] = 'B';
    	        d -= 2;
    	    } else if (d == 0) {
    	        ans[i - 1] = 'C';
    	    } else {
    	        ans[i - 1] = 'A';
    	        d--;
    	    }
    	}
    	Arrays.sort(ans);
    	System.out.println(ans);
    }
}