#include<iostream>
#include<fstream>
#include<sstream>
#include<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<vector>
#include<list>
#include<algorithm>
#include<utility>
#include<complex>
#include<functional>
using namespace std;


#define input_init stringstream ss; string strtoken, token; istringstream is
#define input_line  getline(cin, strtoken);is.str(strtoken);is.clear(istringstream::goodbit)
#define input_token(num) ss.str(""); ss.clear(stringstream::goodbit); getline(is, token, ','); ss << token; ss >> num

const int d[] = { 0, 2, 4, 6, 8, 10 };
int main(void){
	set<string> memo;
	int N;
	cin >> N;
	for (int i = 0; i < N; i++){
		string t;
		cin >> t;
		memo.insert(t);
	}
	string T = "inabameguru";
	int ar[] = { 0, 2, 4, 6, 8, 10 };
	do{
		string tmp = "inabameguru";
		for (int i = 0; i < 6; i++)tmp[d[i]] = T[ar[i]];
			//cout << (" "+!i) << ar[i];
		for (int j = 0; j < 11; j++){
			swap(tmp[j], tmp[max(0, j - 1)]);

			if (memo.count(tmp) == 0){
				cout << tmp << endl;
				return 0;
			}
		}
	} while (next_permutation(ar, ar+6));
	cout << "NO" << endl;
	return(0);
}