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