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

l = [(A[i]-B[i],i) for i in range(N)]
ans = ["B"] * N
l.sort(reverse = True)
for k in range(K):
    _,i = l[k]
    ans[i] = "A"
print("".join(ans))