#import sys
# input = sys.stdin.readline
def mp():return map(int,input().split())
def lmp():return list(map(int,input().split()))
def mps(A):return [tuple(map(int, input().split())) for _ in range(A)]
import math
import bisect
import heapq
from copy import deepcopy as dc
from itertools import accumulate
from collections import Counter, defaultdict, deque
def ceil(U,V):return (U+V-1)//V
def modf1(N,MOD):return (N-1)%MOD+1
inf = int(1e20)
mod = 998244353

n,K = mp()
a = lmp()
b = lmp()
d = [(i,a[i]-b[i]) for i in range(n)]
d.sort(key=lambda x:x[1], reverse=True)
ans = ["B"]*n
for i in range(K):
    ans[d[i][0]] = "A"
print("".join(ans))