n, k = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))

lis = []
for i in range(n):
    li = [a[i] - b[i], i]
    lis.append(li)

lis.sort(reverse=True)
ans = [None] * n

for i in range(k):
    ans[lis[i][1]] = "A"

for i in range(n):
    if ans[i] == None:
        ans[i] = "B"

print("".join(ans))