def main():
  n, k = map(int, input().split())
  A = list(map(int, input().split()))
  B = list(map(int, input().split()))
  if k > n//2:
    A,B=B,A 
    k=n-k

  dp=[[-1000010000]*(k+1) for _ in [0]*(n+1)]
  ans=[['0']*(k+1) for _ in [0]*(n+1)]
  dp[0][0]=0
  for i in range(n):
    for j in range(k+1):
      dp[i+1][j] = max(dp[i+1][j], dp[i][j]+B[i])
      if j<=k and j>0:
        dp[i+1][j]=max(dp[i+1][j], dp[i][j-1]+A[i])
      if dp[i+1][j]==dp[i][j]+B[i]:
        ans[i+1][j]=ans[i][j]+'B'
      else:
        ans[i+1][j]=ans[i][j-1]+'A'
    if i-2>0:
      ans[i-2]=[]

  print(ans[-1][-1][1:])
main()