#include <algorithm>
#include <numeric>
#include <vector>
#include <iostream>
using namespace std;
int main() {
    int n, k; cin >> n >> k;
    vector<int> a(n);
    for (int i = 0; i < n; i++) cin >> a[i];
    for (int i = 0; i < n; i++) { int b; cin >> b; a[i] -= b; }
    vector<int> idx(n);
    iota(idx.begin(), idx.end(), 0);
    sort(idx.begin(), idx.end(), [&a](int i, int j) { return a[i] > a[j]; });
    string ans(n, 'B');
    for (int i = 0; i < k; i++) ans[idx[i]] = 'A';
    cout << ans << '\n';
}