import java.util.*; public class Main { public static void main (String[] args) { Scanner sc = new Scanner(System.in); int n = sc.nextInt(); HashSet exist = new HashSet<>(); for (int i = 0; i < n; i++) { exist.add(sc.next()); } StringSet boins = new StringSet("iaaeuu"); StringSet shiins = new StringSet("nbmgr"); for (String x : boins.set) { for (String y : shiins.set) { String z = merge(x, y); if (!exist.contains(z)) { System.out.println(z); return; } } } System.out.println("NO"); } static String merge(String boin, String shiin) { StringBuilder sb = new StringBuilder(); for (int i = 0; i < boin.length() + shiin.length(); i++) { if (i % 2 == 0) { sb.append(boin.charAt(i / 2)); } else { sb.append(shiin.charAt(i / 2)); } } return sb.toString(); } static class StringSet { char[] base; HashSet set = new HashSet<>(); public StringSet(String s) { base = s.toCharArray(); make(new char[base.length], 0, 0); } void make(char[] arr, int idx, int mask) { if (idx >= arr.length) { set.add(new String(arr)); return; } for (int i = 0; i < base.length; i++) { if ((mask & (1 << i)) != 0) { continue; } arr[idx] = base[i]; make(arr, idx + 1, mask ^ (1 << i)); } } } static boolean getResult(StringBuilder sb, int left, int right, boolean isLeft) { int idx = -1; char ch = (char)0; while (left >= 0 && right < sb.length()) { if (sb.charAt(left) != sb.charAt(right)) { if (idx >= 0) { return false; } if (isLeft) { idx = left + 1; ch = sb.charAt(right); right++; } else { idx = right; ch = sb.charAt(left); left--; } } else { left--; right++; } } if (idx < 0) { if (isLeft) { idx = 0; ch = sb.charAt(sb.length() - 1); } else { idx = sb.length(); ch = sb.charAt(0); } } sb.insert(idx, ch); return true; } }