#hole
N,D=(int(i) for i in input().split())
S=""
if D==2*N:
    for i in range(N):
        S+="B"
elif D>=N:
    D-=N
    N-=D
    for i in range(N):
        S+="A"
    for i in range(D):
        S+="B"
else:
    for i in range(D):
        S+="A"
    N-=D
    for i in range(N):
        S+="C"
print(S)