n, k = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
C = [(a - b, i) for i, (a, b) in enumerate(zip(A, B))]
C.sort(reverse = True)
ans = ["B"] * n
for _, i in C[:k]:
    ans[i] = "A"
print(*ans, sep="")