#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001



int main(){
	
	string bo = "iaaeuu";
	string si = "nbmgr";
	
	sort(bo.begin(),bo.end());
	sort(si.begin(),si.end());
	
	int n;
	cin>>n;
	
	set<string> s;
	rep(i,n){
		string t;
		cin>>t;
		s.insert(t);
	}
	
	do{
		sort(si.begin(),si.end());
		do{
			string t = "";
			rep(i,4){
				t += bo[i];
				t += si[i];
			}
			t += bo.back();
			if(!s.count(t)){
				cout<<t<<endl;
				return 0;
			}
		}
		while(next_permutation(si.begin(),si.end()));
	}while(next_permutation(bo.begin(),bo.end()));
	
	cout<<"NO"<<endl;
	
	return 0;
}