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

import sys
if D == 0:
    print("C" * N)
    exit()
if D <= N:
    ans = "A" * D + "C" * (N - D)
    print(ans)
    exit()
u = D - N
v = N - u
ans = "A" * v + "B" * u
print(ans)