#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[8]={-1,0,1,0,1,1,-1,-1};
const ll dx[8]={0,-1,0,1,1,-1,1,-1};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
int main(){
    string s="aaeiuu",t="bgmnr";
    ll n;cin >> n;
    set<string> st;
    rep(i,n){
        string x;cin >> x;st.insert(x);
    }
    do{
        do{
            rep(j,6){
                string ns;
                ll l=0,r=0;
                rep(i,12){
                    if(i==j*2)continue;
                    if(i%2)ns+=s[l],l++;
                    else ns+=t[r],r++;
                }
                if(st.count(ns))continue;
                cout << ns <<endl;return 0;
            }
        }while(next_permutation(all(t)));
    }while(next_permutation(all(s)));
    cout << "NO" <<endl;
}