import java.util.Scanner;

public class Main{
	
	static final Scanner s=new Scanner(System.in);
	
	public static void main(String[] __){
		int n=s.nextInt(),d=s.nextInt();
		
		StringBuilder sb=new StringBuilder();
		for(int i=n;i>0;i--)
			sb.append('A');
		
		
		sb.delete(0,Math.abs(n-d));
		if(n<d)
			for(int i=d-n;i>0;i--)
				sb.append('B');
		else
			for(int i=n-d;i>0;i--)
				sb.append('C');
		System.out.println(sb.toString());
	}
}