import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	N, D = getlist()
	if D <= N:
		ans = "A" * D + "C" * (N - D)
	else:
		ans = "A" * (2 * N - D) + "B" * (D - N)

	print(ans)
	
if __name__ == '__main__':
	main()