import sys
input = sys.stdin.readline
from collections import *

N, K = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
d = [(i, A[i]-B[i]) for i in range(N)]
d.sort(key=lambda t: t[1], reverse=True)
ans = ['B']*N

for i, _ in d[:K]:
    ans[i] = 'A'

print(''.join(ans))