import sys
readline=sys.stdin.readline
N,K=map(int,readline().split())
A=list(map(int,readline().split()))
B=list(map(int,readline().split()))
AB=[(A[i]-B[i],i) for i in range(N)]
AB.sort(reverse=True)
ans_lst=["B"]*N
for _,i in AB[:K]:
    ans_lst[i]="A"
print(*ans_lst,sep="")