#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)(s); i < (int)(e); ++i)

int main() {
	cin.tie(nullptr);
	ios_base::sync_with_stdio(false);
	
	int N, K;
	cin >> N >> K;
	vector<ll> A(N), B(N);
	rep(i ,0, N) cin >> A[i];
	rep(i, 0, N) cin >> B[i];
	
	priority_queue<pair<ll, int>> que;
	rep(i, 0, N) que.push({A[i] - B[i], i});
	string ans;
	rep(i, 0, N) ans += 'B';
	
	rep(itr, 0, K) {
		ans[que.top().second] = 'A';
		que.pop();
	}
	cout << ans << '\n';
}