## https://yukicoder.me/problems/no/1724
       

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

    a_diff = [(i, A[i] - B[i]) for i in range(N)]
    a_diff.sort(reverse=True, key=lambda x : x[1])
    answer = ["B" for _ in range(N)]
    for i in range(K):
        index = a_diff[i][0]
        answer[index] = "A"

    print("".join(answer))








if __name__ == "__main__":
    main()