n,k=map(int,input().split())
a=list(map(int,input().split()))
b=list(map(int,input().split()))
l=[(a[i]-b[i],i) for i in range(n)]
ans=["B"]*n
l.sort(reverse=True)
for p in range(k):
  _,i=l[p]
  ans[i]="A"
print(''.join(ans))