N,K = map(int,input().split())
A = list(map(int,input().split()))
B = list(map(int,input().split()))
board = []
for i in range(N):
    board.append((A[i]-B[i],i))
board.sort(key = lambda x:x[0])
board.reverse()
ans_A = [False] * N
for i in range(K):
    t,index = board[i]
    ans_A[index] = True
ANS = ''
for i in range(N):
    if ans_A[i]:
        ANS += 'A'
    else:
        ANS += 'B'
print(ANS)