#nullable enable

#region
var (_input, _iter) = (Array.Empty<string>(), 0);
T I<T>() where T : IParsable<T>
{
    while (_iter >= _input.Length) (_input, _iter) = (Console.ReadLine()!.Split(' '), 0);
    return T.Parse(_input[_iter++], null);
}
#endregion

static T[] Range<T>(int n, Func<T> F) => Enumerable.Range(0, n).Select(_ => F()).ToArray();

string Solve()
{
    var n = I<int>();
    var s = I<string>().ToCharArray();
    var f = true;
    for (var i = 0; i < n; i++)
    {
        var c = s[i];
        if (f)
        {
            if (c != 'C') break;
            s[i] = 'A';
        }
        else
        {
            if (c == 'C') break;
            if (c == 'A') s[i] = 'B';
            else s[i] = 'C';
        }
        f = !f;
    }
    return new(s);
}

var t = I<int>();
var ans = Range(t, Solve);
Console.WriteLine(string.Join(Environment.NewLine, ans));