N = int(input())
S = []
candi = set()
for _ in range(N):
    s=input()
    candi.add(s)
s = ["n","b","m","g","r",""]
b = ["i","a","a","e","u","u"]
#print(candi)
s5=[]
b6=[]

for i in range(6):
    if i<5:
        s5.append(i)
    b6.append(i)

import itertools
ss = list(itertools.permutations(s))
bb = list(itertools.permutations(b))
#print(ss)
#sprint(ss)
flag=False
for i in ss:
    for j in bb:
        ca = ""
        for k in range(len(i)):
            ca+=i[k]+j[k]
        if ca not in candi:
            print(ca)
            exit()
print("No")