N,D = map(int,input().split())
S = ""
cnt_a = 0
cnt_b = 0
cnt_c = 0
if D == 0:
    S = 'C' * N
elif D == 1:
    S = 'A' + 'C' * (N-1)
elif D >= N:
    cnt_a = D - 2*(D - N)
    cnt_b = D - N
    cnt_c = N - cnt_a - cnt_b
    S = 'A'*cnt_a + 'B'*cnt_b + 'C'*cnt_c
else:
    cnt_a = D - 2*(N - D)
    cnt_b = N - D
    cnt_c = N - cnt_a - cnt_b
    S = 'A'*cnt_a + 'B' * cnt_b + 'C'*cnt_c
print(S)