#include<bits/stdc++.h>
using namespace std;
#define int long long
#define REP(i,m,n) for(int i=(m);i<(n);i++)
#define rep(i,n) REP(i,0,n)
#define pb push_back
#define all(a) a.begin(),a.end()
#define rall(c) (c).rbegin(),(c).rend()
#define mp make_pair
#define endl '\n'
//#define vec vector<ll>
//#define mat vector<vector<ll> >
#define fi first
#define se second
#define double long double
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll,ll> pll;
//typedef long double ld;
typedef complex<double> Complex;
const ll INF=1e9+7;
const ll MOD=998244353;
const ll inf=INF*INF;
const ll mod=MOD;
const ll MAX=200010;
const double PI=acos(-1.0);
typedef vector<vector<ll> > mat;
typedef vector<ll> vec;



void solve(){
    ll n;cin>>n;
    ll k;cin>>k;
    vector<ll>a(n),b(n);
    rep(i,n)cin>>a[i];
    rep(i,n)cin>>b[i];
    string s="";
    rep(i,n)s+='A';
    vector<pll>p(n);
    rep(i,n)p[i]=mp(-a[i]+b[i],i);
    sort(rall(p));
    rep(i,n-k){
        s[p[i].se]='B';
    }
    cout<<s<<endl;
}

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    solve();
}