package no233;

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.InputMismatchException;
import java.util.NoSuchElementException;

public class Main {
	static IO io = new IO();
	public static void main(String[] args) {
		char[] p = "inabameguru".toCharArray();
		Arrays.sort(p);
		int l = p.length;
		ArrayList<String> lis1 = new ArrayList<>();
		LOOP: do {
			if (!isBoin(p[l-1])) {
				continue;
			}
			boolean siin = false;
			for(int i=0;i<l;i++) {
				if (isBoin(p[i])) {
					siin = false;
				}else{
					if (siin) {
						continue LOOP;
					}
					siin = true;
				}
			}
			lis1.add(new String(p));
		} while(nextPermutation(p));

		IO io = new IO();
		int n = io.nextInt();
		ArrayList<String> lis2 = new ArrayList<>();
		for(int i=0;i<n;i++) {
			lis2.add(io.next());
		}
		Collections.sort(lis2);
		if (lis2.isEmpty()) {
			System.out.println(lis1.get(0));
			return;
		}
		if (lis1.size() == lis2.size()) {
			System.out.println("NO");
			return;
		}else{
			for(int i=0;i<lis1.size();i++) {
				if (i >= lis2.size()) {
					System.out.println(lis1.get(i));
					break;
				}
				if (!lis1.get(i).equals(lis2.get(i))) {
					System.out.println(lis1.get(i));
					break;
				}
			}
		}

	}
	static boolean isBoin(char c) {
		return c == 'a' || c == 'i' || c == 'u' || c == 'e';
	}
	static boolean nextPermutation(char[] p) {
		for(int a=p.length-2;a>=0;--a) {
			if(p[a]<p[a+1]) {
				for(int b=p.length-1;;--b) {
					if(p[b]>p[a]) {
						char t = p[a];
						p[a] = p[b];
						p[b] = t;
						for(++a, b=p.length-1;a<b;++a,--b) {
							t = p[a];
							p[a] = p[b];
							p[b] = t;
						}
						return true;
					}
				}
			}
		}
		return false;
	}

}

class IO extends PrintWriter {
	private final InputStream in;
	private final byte[] buffer = new byte[1024];
	private int ptr = 0;
	private int buflen = 0;

	public IO() { this(System.in);}
	public IO(InputStream source) { super(System.out); this.in = source;}
	private boolean hasNextByte() {
		if (ptr < buflen) {
			return true;
		}else{
			ptr = 0;
			try {
				buflen = in.read(buffer);
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (buflen <= 0) {
				return false;
			}
		}
		return true;
	}
	private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
	private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
	private static boolean isNewLine(int c) { return c == '\n' || c == '\r';}
	public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();}
	public boolean hasNextLine() { while(hasNextByte() && isNewLine(buffer[ptr])) ptr++; return hasNextByte();}
	public String next() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while(isPrintableChar(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	public char[] nextCharArray(int len) {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		char[] s = new char[len];
		int i = 0;
		int b = readByte();
		while(isPrintableChar(b)) {
			if (i == len) {
				throw new InputMismatchException();
			}
			s[i++] = (char) b;
			b = readByte();
		}
		return s;
	}
	public String nextLine() {
		if (!hasNextLine()) {
			throw new NoSuchElementException();
		}
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while(!isNewLine(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	public long nextLong() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		long n = 0;
		boolean minus = false;
		int b = readByte();
		if (b == '-') {
			minus = true;
			b = readByte();
		}
		if (b < '0' || '9' < b) {
			throw new NumberFormatException();
		}
		while(true){
			if ('0' <= b && b <= '9') {
				n *= 10;
				n += b - '0';
			}else if(b == -1 || !isPrintableChar(b)){
				return minus ? -n : n;
			}else{
				throw new NumberFormatException();
			}
			b = readByte();
		}
	}
	public int nextInt() {
		long nl = nextLong();
		if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) {
			throw new NumberFormatException();
		}
		return (int) nl;
	}
	public char nextChar() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		return (char) readByte();
	}
	public double nextDouble() { return Double.parseDouble(next());}
	public int[] nextIntArray(int n) { int[] a = new int[n]; for(int i=0;i<n;i++) a[i] = nextInt(); return a;}
	public long[] nextLongArray(int n) { long[] a = new long[n]; for(int i=0;i<n;i++) a[i] = nextLong(); return a;}
	public double[] nextDoubleArray(int n) { double[] a = new double[n]; for(int i=0;i<n;i++) a[i] = nextDouble(); return a;}
	public void nextIntArrays(int[]... a) { for(int i=0;i<a[0].length;i++) for(int j=0;j<a.length;j++) a[j][i] = nextInt();}
	public int[][] nextIntMatrix(int n,int m) { int[][] a = new int[n][]; for(int i=0;i<n;i++) a[i] = nextIntArray(m); return a;}
	public char[][] nextCharMap(int n,int m) { char[][] a = new char[n][]; for(int i=0;i<n;i++) a[i] = nextCharArray(m); return a;}
	public void close() { super.close(); try {in.close();} catch (IOException e) {}}
}