n,k=map(int,input().split())
A=list(map(int,input().split()))
B=list(map(int,input().split()))
inf=10**9+1
dp=[[0]*(k+1) for _ in range(n+1)]
for i in range(1,n+1):
    dp[i][0]=dp[i-1][0]+B[i-1]
for i in range(1,k+1):
    dp[0][i]=-inf
for i in range(1,n+1):
    for j in range(1,k+1):
        dp[i][j]=max(dp[i-1][j]+B[i-1],dp[i-1][j-1]+A[i-1])
ind=k
val=dp[n][k]
ans=""
for i in range(n-1,-1,-1):
    if val==dp[i][ind-1]+A[i]:
        ans+="A"
        ind-=1
        val-=A[i]
    else:
        ans+="B"
        val-=B[i]
print(ans[::-1])