while True:
    try:
        n=int(input())
        if n==0:break
        list1=input().split()
        list2=[]
        list3=[]
        for i in list1:
            p=sorted(i)
            list2.append("".join(p))
        for j in list2:
            if list2.count(j)==1:list3.append(list1[list2.index(j)])
        list3.sort()
        if len(list3)==0:
            print("None")
        else:
            print(" ".join(list3))
    except EOFError:
        break