using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    public static void Main()
    {
        Solve();
        // Test();
    }
    static void Test()
    {
        var r = new Random();
        var count = 0;
        while (true)
        {
            var n = 8;
            var c = new char[n];
            for (var i = 0; i < n; ++i) c[i] = (char)(r.Next(2) + 'A');
            var s = string.Concat(c);
            // 愚直解
            var s1 = All(s);
            // 作成解
            var s2 = Del(s);
            if (s1 != s2)
            {
                WriteLine(n);
                WriteLine(s);
                WriteLine(s1);
                WriteLine(s2);
                return;
            }
            ++count;
            if (count % 1000 == 0) WriteLine(count);
        }
    }
    static string All(string s)
    {
        var bcnt = s.Count(c => c == 'B');
        var bitmax = (int)Math.Pow(bcnt, bcnt);
        var set = new HashSet<string>();
        set.Add(s);
        for (var b = 0; b < bitmax; ++b)
        {
            var tmp = b;
            var si = s.ToList();
            for (var i = 0; i < bcnt; ++i)
            {
                var cnt = 0;
                for (var j = 0; j + 1 < si.Count; ++j)
                {
                    if (si[j] == 'A')
                    {
                        ++cnt;
                        if (tmp % bcnt == cnt && si[j + 1] == 'B')
                        {
                            si = si.Take(j).Concat(si.Skip(j + 2)).ToList();
                            break;
                        }
                    }
                }
                tmp /= bcnt;
            }
            set.Add(string.Concat(si));
        }
        var ans = new List<string>(set);
        ans.Sort();
        return ans[^1];
    }
    static void Solve()
    {
        var t = NN;
        var ans = new string[t];
        for (var u = 0; u < t; ++u)
        {
            ReadLine();
            var s = ReadLine();
            ans[u] = Del(s);
        }
        WriteLine(string.Join("\n", ans));
    }
    static string Del(string s)
    {
        var stack = new List<(int ac, int bc)>();
        var tac = 0;
        var tbc = 0;
        for (var i = 0; i < s.Length; ++i)
        {
            if (s[i] == 'B' && i + 1 < s.Length && s[i + 1] == 'A')
            {
                ++tbc;
                stack.Add((tac, tbc));
                tac = 0;
                tbc = 0;
            }
            else if (s[i] == 'A') ++tac;
            else ++tbc;
        }
        if (tac != 0 || tbc != 0) stack.Add((tac, tbc));
        // WriteLine(string.Join(" ", stack));
        var st2 = new List<(int ac, int bc)>();
        tac = 0;
        tbc = 0;
        while (stack.Count > 0)
        {
            var cur = stack[^1];
            stack.RemoveAt(stack.Count - 1);
            cur.ac += tac;
            cur.bc += tbc;
            tac = 0;
            tbc = 0;
            if (cur.ac < cur.bc)
            {
                cur.bc -= cur.ac;
                cur.ac = 0;
            }
            else if (cur.bc > 1)
            {
                cur.ac -= cur.bc - 1;
                cur.bc = 1;
            }
            if (cur.ac == 0)
            {
                tac = cur.ac;
                tbc = cur.bc;
            }
            else
            {
                st2.Add(cur);
            }
        }
        if (tac != 0 || tbc != 0) st2.Add((tac, tbc));
        // WriteLine(string.Join(" ", st2));
        var ans = new List<char>();
        while (st2.Count > 0)
        {
            var cur = st2[^1];
            st2.RemoveAt(st2.Count - 1);
            for (var i = 0; i < cur.ac; ++i) ans.Add('A');
            for (var i = 0; i < cur.bc; ++i) ans.Add('B');
        }
        return string.Concat(ans);
    }
}