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

int main() {
    int n, k; cin >> n >> k; int A[n], B[n], i, j;
    for(i = 0; i < n; i++)  cin >> A[i];
    for(i = 0; i < n; i++)  cin >> B[i];
    int cnt = 0; long long sm = 0; int diff[n];
    string str(n, 'a');
    for(i = 0; i < n; i++) {
        if(A[i] >= B[i]) cnt++;
        diff[i] = A[i] - B[i];
    }
    if(k > cnt) {
        priority_queue<pair<int, int>, vector<pair<int, int>>, 
            greater<pair<int, int>>> pq;
        for(i = 0; i < n; i++) {
            if(A[i] >= B[i])        str[i] = 'A';
            else if(B[i] > A[i])    pq.push({diff[i], i});
        }
        i = 0;
        while(i < n - k) {
            pair<int, int> pii = pq.top(); pq.pop();
            str[pii.second] = 'B';
            i++;
        }
        while(!pq.empty()) {
            pair<int, int> pii = pq.top(); pq.pop();
            str[pii.second] = 'A';
        }
    } else {
        priority_queue<pair<int, int>> pq;
        for(i = 0; i < n; i++) {
            if(B[i] >= A[i]) str[i] = 'B';
            else             pq.push({diff[i], i});
        }
        i = 0;
        while(i < k) {
            pair<int, int> pii = pq.top(); pq.pop();
            str[pii.second] = 'A';
            i++;
        }
        while(!pq.empty()) {
            pair<int, int> pii = pq.top(); pq.pop();
            str[pii.second] = 'B';
        }
    }
    cout << str;
    return 0;
}