from itertools import permutations

N=int(input())
S=set()

for _ in range(N):
    S.add(input())

T=set()
for a in permutations(["i","a","a","e","u","u"]):
    for b in permutations(["n","b","m","g","r",""]):
        X=[""]*12
        for i in range(6):
            X[2*i  ]=b[i]
            X[2*i+1]=a[i]

        T.add("".join(X))

U=T-S

if U:
    x=U.pop()
    print(x)
else:
    print("NO")