using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Collections.Generic;
using System.Diagnostics;
using System.Numerics;
using Enu = System.Linq.Enumerable;

class Program
{
    public void Solve()
    {
        int N = Reader.Int();
        var S = Reader.StringArray(N);
        var set = new HashSet<string>();
        foreach(var s in S) set.Add(s);
        char[] V = "iaaeuu".ToCharArray();
        char[] C = "nbmgr".ToCharArray();
        Array.Sort(V);

        do
        {
            Array.Sort(C);
            do
            {
                var sb = new StringBuilder();
                for (int i = 0; i < 5; i++)
                {
                    sb.Append(C[i]);
                    sb.Append(V[i]);
                }
                for (int i = 0; i < sb.Length; i++)
                {
                    var s = sb.ToString().Insert(i, V[5] + "");
                    if (!set.Contains(s)) { Console.WriteLine(s); return; }
                }

            } while (NextPermutation(C));

        } while (NextPermutation(V));

        Console.WriteLine("NO");
    }

    static bool NextPermutation<T>(T[] a)
    {
        Comparer<T> comp = Comparer<T>.Default;
        for (int i = a.Length - 2; i >= 0; i--)
        {
            if (comp.Compare(a[i], a[i + 1]) < 0)
            {
                int j = a.Length - 1;
                while (comp.Compare(a[i], a[j]) >= 0) { j--; }
                T tmp = a[i]; a[i] = a[j]; a[j] = tmp;
                Array.Reverse(a, i + 1, a.Length - 1 - i);
                return true;
            }
        }
        return false;
    }
}


class Entry { static void Main() { new Program().Solve(); } }
class Reader
{
    private static TextReader reader = Console.In;
    private static readonly char[] separator = { ' ' };
    private static readonly StringSplitOptions op = StringSplitOptions.RemoveEmptyEntries;
    private static string[] A = new string[0];
    private static int i;
    private static void Init() { A = new string[0]; }
    public static void Set(TextReader r) { reader = r; Init(); }
    public static void Set(string file) { reader = new StreamReader(file); Init(); }
    public static bool HasNext() { return CheckNext(); }
    public static string String() { return Next(); }
    public static int Int() { return int.Parse(Next()); }
    public static long Long() { return long.Parse(Next()); }
    public static double Double() { return double.Parse(Next()); }
    public static int[] IntLine() { return Array.ConvertAll(Split(Line()), int.Parse); }
    public static int[] IntArray(int N) { return Enu.Range(0, N).Select(i => Int()).ToArray(); }
    public static int[][] IntTable(int H) { return Enu.Range(0, H).Select(i => IntLine()).ToArray(); }
    public static string[] StringArray(int N) { return Enu.Range(0, N).Select(i => Line()).ToArray(); }
    public static string Line() { return reader.ReadLine().Trim(); }
    private static string[] Split(string s) { return s.Split(separator, op); }
    private static string Next() { CheckNext(); return A[i++]; }
    private static bool CheckNext()
    {
        if (i < A.Length) return true;
        string line = reader.ReadLine();
        if (line == null) return false;
        if (line == "") return CheckNext();
        A = Split(line);
        i = 0;
        return true;
    }
}