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

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

AB = list(tuple(zip(A, B, range(N))))
AB.sort(key=lambda x: x[0]-x[1], reverse=True)
result = [None] * N

for k in range(K):
    result[AB[k][2]] = "A"

print("".join([a if a == "A" else "B"  for a in result]))