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

dif = [[0, i] for i in range(n)]
for i in range(n):
    dif[i][0] = A[i] - B[i]
dif.sort(key=lambda x: x[0], reverse=True)
ans = ["B" for _ in range(n)]
for i in range(k):
    ind = dif[i][1]
    ans[ind] = "A"
print("".join(ans))