N,K = map(int,input().split())
A = list(map(int,input().split()))
B = list(map(int,input().split()))
C = []
for i in range(N):
    C.append((A[i]-B[i],i))
C.sort(reverse = True)
ans = [""] * N
for i in range(N):
    if i < K:
        ans[C[i][1]] = "A"
    else:
        ans[C[i][1]] = "B"
print("".join(ans))