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

int main() {
    int t;
    cin >> t;
    while (t--) {
        int N;
        string S;
        cin >> N >> S;
        int sum = 0;
        string ans = "",now = "";
        for(int i = 0; i < N; i++) {
            if(S[i] == 'B') {
                sum++;
                if(sum == 1) {
                    ans += 'B';
                    now = "";
                    sum = 0;
                }
                else {
                    now += 'B';
                }
            }
            else {
                sum--;
                now += 'A';
            }
        }
        cout << ans+now << endl;
    }
}