#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <functional>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <valarray>
#include <vector>

#define N 1000
#define M 1000000007
#define re(i,n) for(int i=0;i<(n);i++)
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define fe(i,n,f) for_each(i,n,f)
#define bw(a,b,c) (((a)<=(b))&&((b)<=(c)))
using namespace std;

typedef long long ll;
typedef unsigned long long ull;

string a="iaaeuu";
string b="nbmgr";

bool fa[6]={0};
bool fb[5]={0};
int n;
set<string> l;

int main(void){
	string s;
	cin>>n;
	re(i,n)cin>>s,l.insert(s);
	sort(a.begin(),a.end());
	sort(b.begin(),b.end());
	do{
		do{
			s="";
			re(i,5){
				s+=b[i];
				s+=a[i];
			}
			re(i,11){
				s="";
				s=s.substr(0,i)+a[5]+s.substr(i);
				if(l.find(s)==l.end())return cout<<s<<endl,0;
			}
			
		}while(next_permutation(b.begin(),b.end()));

	}while(next_permutation(a.begin(),a.end()));

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