from itertools import permutations
consonant = ["", "n", "b", "m", "g", "r"]
vowel = ["i", "a", "a", "e", "u", "u"]
name = set(
    [a+b+c+d+e+f+g+h+i+j+k+l
    for a, c, e, g, i, k in permutations(consonant)
    for b, d, f, h, j, l in permutations(vowel)])

name.difference_update([input() for _ in [0]*int(input())])
print(name.pop() if name else "NO")