n, d = map(int, input().split())

ans = ""

for i in range(n):
    if d > n:
        if i < 2 * n - d:
            ans += "A"
        elif i < n:
            ans += "B"
    else:
        if i < d:
            ans += "A"
        elif i < n:
            ans += "C"

print(ans)