#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";

int n;
set<string> l;
char dfs(int ap,int bp,bool e,string k){ // if(e)boin
	if(ap==6&&bp==5){
		reverse(k.begin(),k.end());
		if(l.find(k)==l.end()){cout<<k<<endl;exit(0);};
	}
	if(e){
		if(ap+1>bp&& ap<6)dfs(ap+1,bp,false,k+a[ap]);
		// return a[ap];
	}else{
		if(ap+1>bp&& ap<6)dfs(ap+1,bp,false,k+a[ap]);
		if(bp<5)dfs(ap,bp+1,true,k+b[bp]);
	}
	return 0;
}

int main(void){
	string s;
	cin>>n;
	re(i,n)cin>>s,l.insert(s);
	dfs(0,0,true,"");
	cout<<"NO"<<endl;

	return 0;
}