import itertools
def isshiin(c):
    return (c !='a' and c!= 'u' and c!='i' and c!='e')

OriginalName ="inabameguru"
Shiin = "nbmgr"
Boin = "iaaeuu"

N = int(input())
S = [] # 使用済み名前のリスト
for x in range(N):
    S.append(input())
flag = False # 終了フラグ
 # すべての子音の並びについて
for s in itertools.permutations(Shiin):
    # すべての母音の並びについて
    for b in itertools.permutations(Boin):
        for i in range(6):
            result = ""
            for j in range(i):
                result += s[j]
                result += b[j]
            result += b[i]
            for j in range(i, 5):
                result += s[j]
                result += b[j+1] 
            if(not result in S):
                flag = True
                break;
        if(flag):
            break;
    if(flag):
        break;
if(flag):
    print(result)
else:
    print("NO")