#include <iostream>
#include <algorithm>
#include <set>
#include <vector>
#include <deque>
#include <cstdlib>

using namespace std;

set<string> st;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)

string s;
string v1 = "bgmnr";
string v2 = "aiue";
int numv1[5] = {1,1,1,1,1}, numv2[4] = {2,1,2,1};

void dfs(bool isshi) {
  if(isshi) {
    rep(i, 4) {
      if(numv2[i] > 0) {
        s.push_back(v2[i]);
        numv2[i]--;
        dfs(false);
        s.pop_back();
        numv2[i]++;
      }
    }
  }
  else {
    bool check = true;
    rep(i, 4) {
      if(numv2[i] > 0) {
        check = false;
        s.push_back(v2[i]);
        numv2[i]--;
        dfs(false);
        s.pop_back();
        numv2[i]++;
      }
    }
    rep(i, 5) {
      if(numv1[i] > 0) {
        check = false;
        s.push_back(v1[i]);
        numv1[i]--;
        dfs(true);
        s.pop_back();
        numv1[i]++;
      }
    }
    if(check) {
      if(!st.count(s)) {
        cout << s << endl;
        exit(0);
      }
    }
  }
}

int main() {

  int N; cin >> N;
  rep(i, N) {
    string s; cin >> s;
    st.insert(s);
  }
  dfs(false);

  cout << "NO\n";

  return 0;
}