N,D = [int(i) for i in input().split()]
ans = []
for i in range(N):
    if D/N == 2:
        ans.append("B")
        N -= 1
        D -= 2
    elif D >= 1:
        ans.append("A")
        N -= 1
        D -= 1
    else:
        ans.append("C")
        N -= 1
        D -= 1
print("".join(ans))