import sys

sys.setrecursionlimit(10 ** 6)
from bisect import *
from collections import *
from heapq import *

int1 = lambda x: int(x) - 1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def SI(): return sys.stdin.readline()[:-1]
def MI(): return map(int, sys.stdin.readline().split())
def MI1(): return map(int1, sys.stdin.readline().split())
def MF(): return map(float, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LF(): return list(map(float, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
dij = [(0, 1), (1, 0), (0, -1), (-1, 0)]

def main():
    def dfs(s="",aa=False,isa=True):
        if len(s)==11:
            if s in ss:return ""
            return s
        if isa:
            for i in range(5):
                if uses[i]:continue
                uses[i]=True
                ret=dfs(s+sc[i],aa,False)
                if ret:return ret
                uses[i]=False
        if (not isa) or (not aa):
            for i in range(6):
                if useb[i]:continue
                useb[i]=True
                ret=dfs(s+bc[i],isa,True)
                if ret:return ret
                useb[i]=False
        return ""

    bc=['a','a','i','u','u','e']
    sc=['n','b','m','g','r']
    useb=[False]*6
    uses=[False]*5
    n=II()
    ss=set()
    for _ in range(n):ss.add(SI())
    ans=dfs()
    if ans:print(ans)
    else:print("NO")

main()