import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

import itertools

N = int(readline())
S = frozenset(read().decode().split())

def gen_consonant_indices():
    for p in itertools.combinations(range(10), 5):
        if all(x + 1 != y for x, y in zip(p, p[1:])):
            yield p

def solve():
    for I in gen_consonant_indices():
        J = [i for i in range(11) if i not in I]
        for perm_1 in itertools.permutations('nbmgr'):
            for perm_2 in itertools.permutations('iaaeuu'):
                name = [None] * 11
                for i, p in zip(I, perm_1):
                    name[i] = p
                for i, p in zip(J, perm_2):
                    name[i] = p
                name = ''.join(name)
                if name in S:
                    continue
                return name
    return 'NO'

print(solve())