#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;

int main(){

    int N;
    cin >> N;
    string S = "iaaeuu", T = "nbmgr", U, V, W;
    vector<int> a(6), b(5);
    set<string> st;
    for (int i=0; i<N; i++){
        cin >> W;
        st.insert(W);
    }
    iota(a.begin(), a.end(), 0); iota(b.begin(), b.end(), 0);

    do{
        do{
            U = "";
            for (int i=0; i<5; i++){
                U += T[b[i]];
                U += S[a[i]];
            }
            for (int i=0; i<11; i+=2){
                V = U.substr(0, i) + S[a[5]] + U.substr(i);
                if (!st.count(V)){
                    cout << V << endl;
                    return 0;
                }
            }
        } while(next_permutation(b.begin(), b.end()));
    } while(next_permutation(a.begin(), a.end()));

    cout << "NO" << endl;

    return 0;
}