//#include <atcoder/all>
//using namespace atcoder;
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(v) v.begin(),v.end()
typedef long long ll;
#define int ll
using vi = vector<int>;
using vs = vector<string>;
using P = pair<int,int>;
template<typename T> bool chmax(T &a, const T b) {if (a < b) {a = b; return true;} else return false; }
template<typename T> bool chmin(T &a, const T b) {if (a > b) {a = b; return true;} else return false; }
const int INF = 1e18;
//using mint = modint1000000007;
//using mint = modint998244353;


signed main() {
   cin.tie(0);
   ios_base::sync_with_stdio(false);
   cout << fixed << setprecision(20);

   int n,k;cin>>n>>k;
   vi a(n),b(n);
   rep(i,n)cin>>a[i];
   rep(i,n)cin>>b[i];
   vector<P> c(n);
   rep(i,n)c[i]={a[i]-b[i],i};
   sort(all(c),greater());
   string ans = string(n,'B');
   rep(i,k)ans[c[i].second]='A';

   cout << ans <<"\n";
   return 0;
}