n, k = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
c = [None] * n
for i in range(n):
    c[i] = (a[i] - b[i], i)
c.sort(reverse=True)
ans = [''] * n
for i in range(n):
    x, j = c[i]
    if i < k:
        ans[j] = 'A'
    else:
        ans[j] = 'B'
print(*ans, sep='')