#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <string>
#include <set>

using namespace std;

int main() {
	int n;
	string name;

	cin >> n;

	set<string> names;
	for (int i = 0; i < n; i++) {
		cin >> name;
		names.insert(name);
	}

	string boin = "nbmgr";
	string shiin = "iaaeuu";
	int n_boin = boin.size();
	int n_shiin = shiin.size();

	sort(boin.begin(), boin.end());
	sort(shiin.begin(), shiin.end());

	name = "inabameguru";
	long long cnt = 0;
	do {
		do {
			for (int i = 0; i < n_shiin; i++) {
				name[2 * i] = shiin[i];
			}
			for (int i = 0; i < n_boin; i++) {
				name[2 * i + 1] = boin[i];
			}
			if (names.count(name) == 0) {
				cout << name << endl;
				return 0;
			}
		} while (next_permutation(boin.begin(), boin.end()));
	} while (next_permutation(shiin.begin(), shiin.end()));

	cout << "NO" << endl;
	return 0;
}