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

int main()
{
	int N, K;
	cin >> N >> K;
	vector<int> A( N ), B( N );
	for( int i = 0; i < N; i++ ) cin >> A[i];
	for( int i = 0; i < N; i++ ) cin >> B[i];

	typedef pair<int, int> P;
	vector<P> v( N );
	for( int i = 0; i < N; i++ ) {
		v[i] = P( B[i] - A[i], i );
	}
	sort( v.begin(), v.end() );
	string ans( N, ' ' );
	for( int i = 0; i < N; i++ ) {
		if( i < K ) ans[ v[i].second ] = 'A';
		else ans[ v[i].second ] = 'B';
	}

	cout << ans << endl;
}