N, S = map(int, raw_input().split())

tmp = S - N
ans = ""
c = 0
if tmp < 0:
    c = tmp * (-1)
    for i in range(S):
        ans += 'A'
    for i in range(N -S):
        ans += 'C'
else :
    for i in range(N - tmp):
        ans += 'A'
    for i in range(tmp):
        ans += 'B'

print ans