n,k=map(int,input().split())
a=list(map(int,input().split()))
b=list(map(int,input().split()))
c=[(a[i]-b[i],i) for i in range(n)]
c.sort()
q=["B"]*n
for i in range(k):
  q[c[~i][1]]="A"
print("".join(q))