import sys
from functools import reduce
import operator


def input(): return sys.stdin.readline().rstrip('\n')


def main():
    n, d = map(int, input().split())
    if d < n:
        print('A' * d + 'C' * (n - d))
    else:
        print('A' * (2 * n - d) + 'B' * (d - n))


if __name__ == '__main__':
    main()