import itertools

se = set()
S = "iaaeuu"
T = "nbmgr"
for s in itertools.permutations(S):    
    for t in itertools.permutations(T):
        name = []
        for ss, tt in zip(s, t):
            name.append(ss + tt)
        name.append(s[-1])
        se.add("".join(name))

n = int(input())
for _ in range(n):
    S = input()
    if S in se:
        se.remove(S)

for s in se:
    print(s)
    exit()
print("NO")