n, k = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))

X = []
for i, (a, b) in enumerate(zip(A, B)):
    X.append((a-b,i))
X.sort(key=lambda x: -x[0])
ans = ['B']*n
for i in range(k):
    _, j = X[i]
    ans[j] = 'A'
print(''.join(ans))