from itertools import permutations

A = ['a', 'a', 'i', 'u', 'u', 'e']
B = ['n', 'b', 'm', 'g', 'r']

ans_set = set()
for P in permutations(range(11), 5):
    sortP = sorted(P)
    flag = True
    cnt = 0
    for i in range(4):
        if sortP[i + 1] - sortP[i] == 1:
            flag = False
            break
        elif sortP[i + 1] - sortP[i] == 3:
            cnt += 1
            if cnt == 2:
                flag = False
                break
        elif sortP[i + 1] - sortP[i] > 3:
            flag = False
            break
    if cnt == 1:
        if sortP[0] > 0:
            flag = False
    if sortP[4] == 10:
        flag = False
    if not flag:
        continue
    S = ['' for _ in range(11)]
    for i in range(5):
        S[P[i]] = B[i]
    Idx = []
    for i in range(11):
        if S[i] == '':
            Idx.append(i)
    for Q in permutations(range(6)):
        Sc = S[:]
        for i in range(6):
            Sc[Idx[Q[i]]] = A[i]
        ans_set.add(''.join(Sc))

remove_set = set()
n = int(input())
for _ in range(n):
    remove_set.add(input())
for ans in ans_set:
    if ans not in remove_set:
        print(ans)
        exit()
print("NO")