#include <iostream>
#include <cstdint>
#include <vector>
#include <algorithm>
#include <functional>

using namespace std;

int main()
{
	cin.tie(nullptr);
	ios::sync_with_stdio(false);

	int32_t N, K, i;
	cin >> N >> K;
	vector<int32_t> A(N), B(N);
	for (i = 0; i != N; ++i) cin >> A[i];
	for (i = 0; i != N; ++i) cin >> B[i];

	vector<pair<int32_t, int32_t>> gap(N);
	int64_t bias = 0;
	for (i = 0; i != N; ++i)
	{
		gap[i] = { A[i] - B[i], i };
		bias -= B[i];
	}

	string S;
	S.resize(N, 'B');
	sort(gap.begin(), gap.end(), greater<pair<int32_t, int32_t>>());
	for (i = 0; i != K; ++i)
		S[gap[i].second] = 'A';

	cout << S << '\n';
	return 0;
}