#include <iostream>
#include <algorithm>
#include <set>
#include <vector>
#include <set>
#include <queue>
#include <tuple>
#include <map>
#define se second
#define fi first
using namespace std;
using ll = long long;
using ull = unsigned long long;

#define rep(i,n) for(long long i = 0; i < (int)n; i++)

#define FOR(i, m, n) for(long long i = (m);i < (n); ++i)
#define ALL(obj) (obj).begin(),(obj).end()
#define SPEED cin.tie(0);ios::sync_with_stdio(false);

template<class T> using V = vector<T>;
template<class T, class U> using P = pair<T, U>;
template<class T> using PQ = priority_queue<T>;
template<class T> using PQR = priority_queue<T,vector<T>,greater<T>>;


void print(V<ll> ar) {
    for(auto x: ar)cout << x << " " ;
    cout << endl;
}

ll gcd(ll a, ll b) {
    if (a<b)return gcd(b,a);
    if (b==0)return a;
    return gcd(b, a%b);
}

ll mpow(ll x, ll n, ll p) {
    ll r = 1;
    while (n>0) {
        if (n%2) {
            r*=x;
            r%=p;
        }
        x *= x;
        x %= p;
        n/=2;
    }
    return r;
}
const ll mod = 998244353;

V<P<ll,int>> facts(ll n) {
    V<P<ll,int>> res;
    if (n==1)return res;

    for(int x = 2; x*x<=n; x++) {
        if (n%x==0) {
            int p = 0;
            while (n%x==0) {
                p+=1;
                n/=x;
            }
            res.emplace_back(P<ll,int>(x, p));
        }
    }
    if (n!=1) {
        res.emplace_back(P<ll,int>(n, 1));
    }
    return res;
}


int main()
{
    int n,k;cin >> n >> k;
    V<ll> a(n),b(n);
    rep(i, n)cin >> a[i];
    rep(i, n)cin >> b[i];
    V<P<ll, int>> p(n);
    rep(i, n) {
        p[i].se = i;
        p[i].fi = b[i]-a[i];
    }
    sort(p.begin(), p.end());
    V<int> ans(n);
    rep(i, n) {
        if (i<k)ans[p[i].se] = 0;
        else ans[p[i].se] = 1;
    }
    rep(i, n) {
        if (ans[i])cout << "B";
        else cout << "A";
    }
    cout << endl;
}