import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Scanner;

public class Main {
	
	public static final long MOD = 1000000000000l;

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int N = sc.nextInt();
		int D = sc.nextInt();
		
		StringBuilder sb = new StringBuilder();
		
		while(N < D){
			sb.append('B');
			D -= 2; N -= 1;
		}
		
		while(N > D){
			sb.append('C');
			N -= 1;
		}
		
		while(N != 0){
			sb.insert(0, 'A');
			N -= 1; D -= 1;
		}
		
		System.out.println(sb.toString());
	}
}