mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

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

    C = []
    for i in range(N):
        C.append((B[i] - A[i], i))
    C.sort(key=lambda x: x[0])
    ans = ["B"] * N
    for i in range(K):
        ans[C[i][1]] = "A"
    print("".join(ans))


if __name__ == '__main__':
    main()