#include <bits/stdc++.h>

using namespace std;
#define rep(i,n) for(long long i=0;i<n;++i)
#define rep1(i,n) for(long long i=1;i<=n;++i)
#define rrep(i,n) for(long long i=n-1;i>=0;--i)
#define debug(output) if(debugFlag)cout<<#output<<"= "<<output<<endl
using lint = long long;
typedef pair<int,int> P;
const bool debugFlag=true;
const lint linf=1.1e18;const lint inf=1.01e9;
constexpr int MOD=1000000007;
template<class T>bool chmax(T &a, const T &b) { if(a < b){ a = b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if(a > b){ a = b; return 1; } return 0; }

signed main(){
  int n,k;cin>>n>>k;
  vector<lint> a(n),b(n);
  rep(i,n)cin>>a[i];
  rep(i,n)cin>>b[i];
  string res;
  priority_queue<pair<lint,int>> que;
  rep(i,n)que.push({a[i]-b[i],i});
  rep(i,n)res+='B';
  rep(i,k){
    res[que.top().second]='A';que.pop();
  }
  cout<<res<<"\n";
  return 0;
}