#include <iostream>
#include <algorithm>
#include <set>
#include <vector>
using namespace std;

int N;
set<string> names;

char vowel[6] = {'i', 'a' ,'a', 'e', 'u', 'u'},
     consonant[5] = {'n', 'b', 'm', 'g', 'r'};

bool v_used[6], c_used[5];

string answer;

void DFS(int v_num, int c_num, bool prev_is_cons, string accum) {
    if (answer != "" || v_num < c_num - 1 + prev_is_cons) return;

    if (v_num == 0 && c_num == 0) {
        if (!prev_is_cons && names.find(accum) == names.end()) {
            answer = accum;
        }
        return;
    }

    for (int i = 0; i < 6; i++) {
        if (!v_used[i]) {
            v_used[i] = true;
            accum.push_back(vowel[i]);
            DFS(v_num - 1, c_num, false, accum);
            v_used[i] = false;
            accum.pop_back();
        }
    }

    if (prev_is_cons) return;

    for (int i = 0; i < 5; i++) {
        if (!c_used[i]) {
            c_used[i] = true;
            accum.push_back(consonant[i]);
            DFS(v_num, c_num - 1, true, accum);
            c_used[i] = false;
            accum.pop_back();
        }
    }
}

void Solve() {
    answer = "";
    DFS(6, 5, false, "");
    if (answer == "") cout << "NO" << endl;
    else cout << answer << endl;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    cin >> N;

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

    Solve();

    return 0;
}