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

dp = [[-1000010000]*(k+1) for _ in range(n+1)]
ans = [['0']*(k+1) for _ in range(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'

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