using System;
using System.Linq;

class I
{
	static void Main() => Console.WriteLine(Solve());
	static object Solve()
	{
		var n = int.Parse(Console.ReadLine());
		var s = Console.ReadLine();

		if (s.Contains('H')) return -1;
		if (!s.Contains('Q')) return -1;

		var qc = s.Count(c => c == 'Q');

		var rc = (int)Math.Round(Math.Sqrt(qc));
		if (rc * rc != qc) return -1;
		if (n % rc != 0) return -1;

		var sublength = n / rc;
		var sub = s[..sublength];

		for (int i = 0; i < rc; i++)
			if (s[(i * sublength)..((i + 1) * sublength)] != sub) return -1;
		return sub;
	}
}