# -*- coding: utf-8 -*-
"""
No.501 穴と文字列
https://yukicoder.me/problems/no/501

"""
import sys
from sys import stdin
input = stdin.readline


def solve(N, D):
    excess = D - N

    if excess >= 0:
        ans = 'A' * (N - excess)
        ans += 'B' * excess
    else:
        ans = 'A' * (N + excess)
        ans += 'C' * -excess

    return ans


def main(args):
    N, D = map(int, input().split())
    ans = solve(N, D)
    print(ans)


if __name__ == '__main__':
    main(sys.argv[1:])