N,K = map(int,input().split())
lsA = list(map(int, input().split()))
lsB = list(map(int, input().split()))
lsALL = []
for i in range(N):
    lsALL.append((lsA[i]-lsB[i],i))
lsALL.sort(reverse=True)
ansls = ['B' for _ in range(N)]
for i in range(K):
    ansls[lsALL[i][1]] = 'A'
print(*ansls,sep='')