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,6))
bb = list(itertools.permutations(b,6))
#print(ss)
flag=False
for i in ss:
    for j in bb:
        ca = []
        for k in range(len(i)):
            ca.append(i[k]+j[k])
        ccc = list(itertools.permutations(ca,6))
        for cccc in ccc:
            candidate = "".join(cccc)
            if candidate not in candi:
                print(candidate)
                exit()
print("No")