#include<bits/stdc++.h>
#include<iostream>
using namespace std;
using LL = long long;
using P = pair<int,int>;
using Graph = vector<vector<int>>;
const int INF = 1 << 29;
const long long LINF = 1LL << 60;
#define all(x) (x).begin(), (x).end()
#define rep(i,n) for(int i = 0; i < (n); ++i)
template<class T>void chmin(T&a, T b){if(a > b) a = b;}
template<class T>void chmax(T&a, T b){if(a < b) a = b;}


int main(){
	int N, K; cin >> N >> K;
	vector<int> A(N), B(N);
	for(int i = 0; i < N; ++i) cin >> A[i];
	for(int i = 0; i < N; ++i) cin >> B[i];

	string ans = "";
	for(int i = 0; i < N; ++i) ans += "A";
	vector<pair<int, int>> A_B(N);
	for(int i = 0; i < N; ++i){
		A_B[i] = make_pair(A[i]-B[i], i);
	}
	sort(A_B.begin(), A_B.end());
	for(int i = 0; i < N-K; ++i){
	   ans[A_B[i].second] = 'B';
	}
	cout << ans << endl;

}