#include<bits/stdc++.h>

using namespace std;
using ll = long long;
using ld = long double;

bool comp(pair<ll,ll> a,pair<ll,ll> b){
	if(a.second < b.second) return true;
	return false;
}

int main(){
	ll n,k;
	cin >> n >> k;
	vector<ll> a(n),b(n);
	vector<pair<ll,ll>> diff(n);
	string ans = "";
	for(int i=0;i < n;i++) cin >> a[i];
	for(int i=0;i < n;i++) cin >> b[i];
	for(int i=0;i < n;i++){
		ans += 'A';
		diff[i] = {i,a[i]-b[i]};
	}
	

	sort(diff.begin(),diff.end(),comp);

	for(int i=0;i < n-k;i++){
		ans[diff[i].first] = 'B';
	}
	cout << ans << endl;
	return 0;
}