#include <bits/stdc++.h>
#define rep(i, l, r) for (int i = (l); i < (r); i++)
using namespace std;

typedef long long ll;

int main() {
    int N, K;
    cin >> N >> K;
    vector<int> A(N), B(N);
    rep(i, 0, N) cin >> A[i];
    rep(i, 0, N) cin >> B[i];
    vector<pair<int, int>> C(N);
    rep(i, 0, N) {
        C[i] = make_pair(B[i] - A[i], i);
    }
    sort(C.begin(), C.end());
    vector<char> ans(N, 'B');
    rep(i, 0, K) ans[C[i].second] = 'A';
    rep(i, 0, N) cout << ans[i];
    cout << endl;
}