import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;

public class Main {
	static HashSet<String> set = new HashSet<String>();
	static char[] ch = {'m', 'n', 'r', 'g', 'b'};
	static char[] mo = {'u', 'i', 'a', 'a', 'u', 'e'};
	public static void main(String[] args) throws NumberFormatException,
	IOException {
		ContestScanner in = new ContestScanner();
		int n = in.nextInt();
		if(n >= 237600){
			System.out.println("NO");
			return;
		}
		for(int i=0; i<n; i++){
			String s = in.nextToken();
			set.add(s);
		}
		if(set.size() >= 237600 || !dfsCH(0, pc, 0)){
			System.out.println("NO");
		}else{
			System.out.println(res);
		}
	}
	
	static String res = null;
	static int[] pc = new int[5];
	static int[] pm = new int[6];
	static boolean dfsCH(int dpt, int[] p, int used){
		if(dpt == 5){
			if(dfsM(0, pm, 0)) return true;
			return false;
		}
		for(int i=0; i<5; i++){
			if((used&1<<i)>0) continue;
			p[dpt] = i;
			if(dfsCH(dpt+1, p, used|1<<i)) return true;
		}
		return false;
	}
	
	static boolean dfsM(int dpt, int[] p, int used){
		if(dpt == 6){
			if(make()) return true;
			return false;
		}
		for(int i=0; i<6; i++){
			if((used&1<<i)>0) continue;
			p[dpt] = i;
			if(dfsM(dpt+1, p, used|1<<i)) return true;
		}
		return false;
	}
	
	static boolean make(){
		List<Character> list = new LinkedList<Character>();
		for(int i=0; i<5; i++){
			list.add(ch[pc[i]]);
			list.add(mo[pm[i]]);
		}
		int size = list.size();
		for(int i=0; i<size; i++){
			list.add(i, mo[pm[5]]);
			StringBuilder sb = new StringBuilder();
			for(char c: list) sb.append(c);
			if(!set.contains(sb.toString())){
				res = sb.toString();
				return true;
			}
			list.remove(i);
		}
		return false;
	}
}

class Timer{
	long time;
	public void set(){
		time = System.currentTimeMillis();
	}
	
	public long stop(){
		return System.currentTimeMillis()-time;
	}
}

class Node{
	int id;
	ArrayList<Node> edge = new ArrayList<Node>();
	public Node(int id) {
		this.id = id;
	}
	public void createEdge(Node node) {
		edge.add(node);
	}
}

class MyComp implements Comparator<int[]> {
	final int idx;
	public MyComp(int idx){
		this.idx = idx;
	}
	public int compare(int[] a, int[] b) {
		return a[idx] - b[idx];
	}
}

class Reverse implements Comparator<Integer> {
	public int compare(Integer arg0, Integer arg1) {
		return arg1 - arg0;
	}
}


class ContestWriter {
	private PrintWriter out;

	public ContestWriter(String filename) throws IOException {
		out = new PrintWriter(new BufferedWriter(new FileWriter(filename)));
	}

	public ContestWriter() throws IOException {
		out = new PrintWriter(System.out);
	}

	public void println(String str) {
		out.println(str);
	}
	
	public void println(Object obj) {
		out.println(obj);
	}

	public void print(String str) {
		out.print(str);
	}
	
	public void print(Object obj) {
		out.print(obj);
	}

	public void close() {
		out.close();
	}
}

class ContestScanner {
	private BufferedReader reader;
	private String[] line;
	private int idx;

	public ContestScanner() throws FileNotFoundException {
		reader = new BufferedReader(new InputStreamReader(System.in));
	}

	public ContestScanner(String filename) throws FileNotFoundException {
		reader = new BufferedReader(new InputStreamReader(new FileInputStream(
				filename)));
	}

	public String nextToken() throws IOException {
		if (line == null || line.length <= idx) {
			line = reader.readLine().trim().split(" ");
			idx = 0;
		}
		return line[idx++];
	}
	
	public String readLine() throws IOException{
		return reader.readLine();
	}

	public long nextLong() throws IOException, NumberFormatException {
		return Long.parseLong(nextToken());
	}

	public int nextInt() throws NumberFormatException, IOException {
		return (int) nextLong();
	}

	public double nextDouble() throws NumberFormatException, IOException {
		return Double.parseDouble(nextToken());
	}
}