#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<string> se;

	rep(i, n){
		string t;
		cin >> t;
		se.insert(t);
	}
	do{
		do{

			rep(i, 5){
				string t;
				int tb = 0, tc = 0;

				rep(j, 11){
					if ((j % 2 == 0) && tc < 5){
						t += cs[tc++];
					}
					if (j % 2 && tb < 6){
						t += bs[tb++];
						if ((i * 2) + 1 == j)t += bs[tb++];
					}
				}
				if (!se.count(t)){
					cout << t << endl;
					return 0;
				}
			}

			string t;

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


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

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





	cout << "NO" << endl;

	return 0;
}