lib C
  fun strtoll(s : UInt8*, p : UInt8**, b : Int32) : Int64
end

class String
  def to_i64
    C.strtoll(self, nil, 10)
  end
end

vowel, cons = "iaaeuu", "nbmgr"
size = vowel.size + cons.size

n = read_line.to_i
s = (1..n).map { read_line }.to_set

puts (0...6).flat_map { |vowel_pos|
  f = [0, 1] * 5
  f.insert({0, vowel_pos * 2 - 1}.max, 1)
  Array.product(vowel.chars.permutations, cons.chars.permutations).map { |(v, c)|
    (0...11).map { |i| (f[i] == 0 ? c : v).shift(1)[0] }.join
  }
}.find { |str| !s.includes?(str) } || "NO"