from itertools import permutations

N = int(input())
S = set([input() for _ in range(N)])
A = ["","n","b","m","g","r"]
B = ["i","a","a","e","u","u"]
for X in permutations(range(6),6):
    for Y in permutations(range(6),6):
        tmp = []
        for i in range(6):
            tmp.append(A[X[i]])
            tmp.append(B[Y[i]])
        tmp = "".join(tmp)
        if tmp not in S:
            print(tmp)
            exit()