#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll MOD = 1000000007;
using P = pair<ll,int>;
#define rep(i, n) for(int i = 0; i < n; i++)
#define all(x) (x).rbegin(),(x).rend()

int main(){
    int n,k;
    cin >> n >> k;
    vector<P> dif(n);
    rep(i,n) cin >> dif[i].first;
    rep(i,n){
        ll b;
        cin >> b;
        dif[i].first -= b;
        dif[i].second = i;
    }
    sort(all(dif));
    vector<bool> ans(n,false);
    rep(i,k){
        ans[dif[i].second] = true;
    }
    rep(i,n){
        if(ans[i]) cout << 'A';
        else cout << 'B';
    }
    cout << endl;
    return 0;
}