#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
set<string> st;
string c[6] = { "","n","b","m","g","r" };
string v[6] = { "i","a","a","e","u","u" };
vector<int> vec = { 0,1,2,3,4,5 }, vec1 = { 0,1,2,3,4,5 };
int main() {
	int n;
	cin >> n;
	for (int i = 0; i < n; i++) {
		string s;
		cin >> s;
		st.insert(s);
	}
	if (st.find("inabameguru") == st.end()) {
		cout << "inabameguru" << endl;
		return 0;
	}
	while (next_permutation(vec.begin(), vec.end())) {
		while (next_permutation(vec1.begin(), vec1.end())) {
			string ans = "";
			for (int i = 0; i < 6; i++) {
				ans += c[vec[i]];
				ans += v[vec1[i]];
			}
			if (st.find(ans) == st.end()) {
				cout << ans << endl;
				return 0;
			}
		}
	}
	cout << "NO" << endl;
}