from itertools import permutations, product
N = int(input())
a = [input() for i in range(N)]
vow = 'iaaeuu'
con = ' nbmgr'
vow_all = list(map(''.join, permutations(vow)))
con_all = list(map(''.join, permutations(con)))
vow_size = len(vow_all)
con_size = len(con_all)
all_list = []
for i in range(vow_size):
    for j in range(con_size):
        strings = ''
        for k in range(6):
            strings = strings + con_all[j][k] + vow_all[i][k]
        all_list.append( strings.replace(' ','') )

all_list = set(all_list)
a = set(a)
all_list -= a

if len(all_list) == 0:
    print('NO')
else:
    print('%s' % all_list.pop())