while True:
    n=int(input())
    if n==0:
        break
    s=input().split()
    i=0
    s1=[]
    while i<len(s):
        a=list(s[i])
        a.sort()
        b="".join(a)
        s1.append(b)
        i+=1
    s2=[]
    j=0
    while j<len(s1):
        if s1.count(s1[j])==1:
            s2.append(s[j])
        j+=1
    s2.sort()
    if len(s2)==0:
        print("None")
    else:
        for m in s2:
            print(m,end=" ")
        print()