def main():
    N, K = map(int, input().split())
    A = list(map(int, input().split()))
    B = list(map(int, input().split()))

    pattern = ["" for _ in range(N)]
    diff = [(a - b, idx) for idx, (a, b) in enumerate(zip(A, B))]
    diff.sort(reverse=True)
    for idx, (_, elm_idx) in enumerate(diff):
        if idx < K:
            pattern[elm_idx] = "A"
        else:
            pattern[elm_idx] = "B"

    print("".join(pattern))


if __name__ == "__main__":
    main()