#!/usr/bin/env python3

from pprint import pprint
from sys import setrecursionlimit, stdin
from typing import Dict, Iterable, Set

INF: int = 1 << 62
setrecursionlimit(1_000_000)


def inputs(type_=int):
    ins = input().split()
    ins = [x for x in ins if x != '']

    if isinstance(type_, Iterable):
        return [t(x) for t, x in zip(type_, ins)]
    else:
        return list(map(type_, ins))


def input_(type_=int):
    a, = inputs(type_)
    return a


inputi = input_


def inputstr():
    return input_(str)


def answer(res) -> None:
    print(res)
    exit()


# start coding
n, k = inputs()
A = inputs()
B = inputs()
C = [a-b for (a, b) in zip(A, B)]
C = [(c, i) for (i, c) in enumerate(C)]
C.sort(reverse=True)
# print(C[:k])
ps = []
for c, i in C[:k]:
    ps.append(i)
ps = set(ps)

res = [None] * n
for i in range(n):
    if i in ps:
        res[i] = 'A'
    else:
        res[i] = 'B'

print(''.join(res))