import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N,D = map(int,read().split())

if D <= N:
    answer = 'A' * D + 'C' * (N-D)
else:
    answer = 'A' * (N+N-D) + 'B' * (D-N)

print(answer)