#include <iostream>
#include <algorithm>
#include <string>
using namespace std;

pair<int, int> p[200009];

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	int n, k; cin >> n >> k;
	string ans = "";
	for (int i = 0; i < n; i++) {
		int a; cin >> a;
		p[i].first = a;
		p[i].second = i;
		ans += "B";
	}
	for (int i = 0; i < n; i++) {
		int a; cin >> a;
		p[i].first -= a;
	}
	sort(p, p + n);
	for (int i = n - 1; i >= n - k; i--)
		ans[p[i].second] = 'A';
	cout << ans << '\n';
	return 0;
}