import std.stdio;
import std.array;
import std.string;
import std.conv;
import std.algorithm;
import std.typecons;
import std.range;

void main() {
  int N = readln().chomp.to!int;
  bool[string] used;
  foreach (i; iota(N))
    used[readln().chomp] = true;

  string s1 = "iaaeuu";
  string s2 = "nbmgr";
  auto p1 = [0, 1, 2, 3, 4, 5];
  do {
    auto p2 = [0, 1, 2, 3, 4];
    do {
      string s3 = "";
      string s4 = "";
      foreach (i; iota(5)) {
        s3 ~= s1[p1[i]];
        s3 ~= s2[p2[i]];
        s4 ~= s2[p2[i]];
        s4 ~= s1[p1[i]];
      }
      if (!(s3~s1[p1[5]] in used)) {writeln(s3~s1[p1[5]]); return;}
      if (!(s4~s1[p1[5]] in used)) {writeln(s4~s1[p1[5]]); return;}
    } while(nextPermutation(p2));
  } while(nextPermutation(p1));
  
  writeln("NO");
}