#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <functional>
#include <queue>
#include <set>

using namespace std;

#define For(i,a,b) for(int i = (a);i < (b);i++)
#define rep(i,n) For(i,0,n)

const int dx[8] = { 1, 0, -1, 0, 1, 1, -1, -1 }, dy[8] = { 0, -1, 0, 1, -1, 1, -1, 1 };
string dc[8] = { ">", "v", "<", "^", ">^", ">v", "<^", "<v" };

typedef pair<int, int> P;

int main(){

	int n;
	cin >> n;

	string s = "inabameguru";
	string bs = "iaaeuu";
	string cs = "nbmgr";
	sort(bs.begin(), bs.end());
	sort(cs.begin(), cs.end());

	set<pair<string,string>> se;

	rep(i, n){
		string t;
		cin >> t;
		string b;
		string c;
		rep(j, t.size()){
			if (j % 2){
				c += t[j];
			}
			else{
				b += t[j];
			}
		}
		se.insert(make_pair(b, c));
	}
	do{

		do{

			if (!se.count(make_pair(bs, cs))){
				rep(j, 11){
					if (j % 2){
						cout << cs[j / 2];
					}
					else{
						cout << bs[j / 2];
					}
				}
				cout << endl;
				return 0;
			}

		} while (next_permutation(bs.begin(), bs.end()));

	} while (next_permutation(cs.begin(), cs.end()));


	cout << "NO" << endl;

	return 0;
}