import sys
input = sys.stdin.readline

N,K=map(int,input().split())
A=list(map(int,input().split()))
B=list(map(int,input().split()))

X=[(A[i]-B[i],i) for i in range(N)]
X.sort(reverse=True)

ANS=["B"]*N

for i in range(K):
    ANS[X[i][1]]="A"

print("".join(ANS))