import sequtils,algorithm,math,tables
import sets,intsets,queues,heapqueue,bitops,strutils
template times*(n:int,body) = (for _ in 0..<n: body)
template `max=`*(x,y) = x = max(x,y)
template `min=`*(x,y) = x = min(x,y)

proc getchar_unlocked():char {. importc:"getchar_unlocked",header: "<stdio.h>" .}
proc scan(): int =
  while true:
    let k = getchar_unlocked()
    if k < '0': break
    result = 10 * result + k.ord - '0'.ord

let n = scan()
var used = initSet[string]()
n.times: used.incl stdin.readLine()
var S = "inabameguru".sorted(cmp).join("")
while true:
  var ok = true
  const consonant = ['n','b','m','g','r']
  for i in 1..<S.len:
    if S[i] in consonant and S[i-1] in consonant:
      ok = false
      break
  if ok and S[^1] in consonant : ok = false
  if ok and S notin used:
    quit S, 0
  if not S.nextPermutation(): break
echo "NO"