import heapq
N,K = map(int,input().split())
A = list(map(int,input().split()))
B = list(map(int,input().split()))
use = [True]*N
C = []

for i,(a,b) in enumerate(zip(A,B)):
    heapq.heappush(C,(-(b-a),i))

for i in range(N-K):
    value,index = heapq.heappop(C)
    use[index]=False

ans = ''.join(list(map(lambda x:'A'if x else 'B',use)))
print(ans)