#include <bits/stdc++.h>
using namespace std;

int n, k;
long long a[200000], b[200000];
pair<long long, int> c[200000];
char s[200001];

int main()
{
	cin >> n >> k;

	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++)
		c[i] = { a[i] - b[i], i };

	sort(c, c + n);

	for (int i = 0; i < n - k; i++)
		s[c[i].second] = 'B';

	for (int i = n - k; i < n; i++)
		s[c[i].second] = 'A';

	cout << s << endl;	
}