N,K = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
L = []
for i in range(N):
    L.append([A[i]-B[i],i])
L = sorted(L, reverse=True, key=lambda x: x[0])
ANS = ['B']*N
for i in range(K):
    ANS[L[i][1]]='A'
print(''.join(map(str, ANS)))