import sys
input = sys.stdin.readline
from itertools import *

N = int(input())
S = set()
for _ in range(N):
    S.add(input().rstrip())

L = [[1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1],
     [0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1],
     [0, 1, 0, 1, 1, 0, 1, 0, 1, 0, 1],
     [0, 1, 0, 1, 0, 1, 1, 0, 1, 0, 1],
     [0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 1],
     [0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1],]
for t1 in permutations(["n", "b", "m", "g", "r"]):
    for t2 in set(permutations(["i", "a", "a", "e", "u", "u"])):
        for k in range(6):
            temp = []
            i1, i2 = 0, 0
            for i in range(11):
                if L[k][i]:
                    temp.append(t2[i2])
                    i2 += 1
                else:
                    temp.append(t1[i1])
                    i1 += 1
            temp = "".join(temp)
            if temp not in S:
                print(temp)
                exit()

print("NO")