#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;
using ll = long long;

int main(){

    ll N, K;
    cin >> N >> K;
    vector<ll> A(N);
    vector<pair<ll, ll>> B(N);
    string S(N, 'A');
    for (int i=0; i<N; i++) cin >> A[i];
    for (int i=0; i<N; i++){
        cin >> B[i].first;
        B[i].first -= A[i];
        B[i].second = i;
    }
    sort(B.begin(), B.end(), greater<pair<ll, ll>>());
    for (int i=0; i<N-K; i++){
        S[B[i].second] = 'B';
    }
    cout << S << endl;


    return 0;
}