#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cctype>
#include<cstdlib>
#include<algorithm>
#include<bitset>
#include<vector>
#include<list>
#include<deque>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<sstream>
#include<fstream>
#include<iomanip>
#include<ctime>
#include<complex>
#include<functional>
#include<climits>
#include<cassert>
#include<iterator>
#include<unordered_map>
using namespace std;

int n;
set<string> s;
int main(){
	cin >> n;
	for (int i = 0; i < n; i++){
		string k;
		cin >> k;
		s.insert(k);
	}
	string t = "inabameguru";
	vector<char> a;
	vector<char> b;
	a.clear();
	b.clear();
	for (int i = 0; i < t.size(); i++){
		if (i % 2){
			b.push_back(t[i]);
		}
		else{
			a.push_back(t[i]);
		}
	}
	sort(a.begin(), a.end());
	sort(b.begin(), b.end());
	do{
		sort(b.begin(), b.end());
		do{
			string k;
			k.clear();
			bool f = false;
			for (int i = 0; i < a.size() + b.size(); i++){
				if (i % 2){
					k.push_back(b[i / 2]);
				}
				else{
					k.push_back(a[i / 2]);
				}
			}
			if (s.count(k) == 0){
				cout << k << endl;
				return 0;
			}
			k.clear();
			for (int i = 0; i < a.size() + b.size(); i++){  //i,i+1=a
				k.clear();
				int ind = 0;
				int indd = 0;
				bool flag = false;
				if (i != 0){
					flag = true;
				}
				for (int j = 0; j < a.size() + b.size(); j++){
					if (flag){
						k.push_back(b[indd]);
						indd++;
					}
					else{
						k.push_back(a[ind]);
						ind++;
					}
					if (j == i - 1){
						flag = false;
						continue;
					}
					if (j == i){
						flag = false;
						continue;
					}
					flag ^= 1;
				}
				if (s.count(k)){
					continue;
				}
				if (find(a.begin(), a.end(), k.back()) == a.end()){
					continue;
				}
				cout << k << endl;
				return 0;
			}
		} while (next_permutation(b.begin(), b.end()));
	} while (next_permutation(a.begin(), a.end()));
	puts("NO");
	return 0;
}