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 = i+1
    s2 = []
    i = 0
    while i<len(s1):
        if s1.count(s1[i]) == 1:
            s2.append(s[i])
        i = i+1
    s2.sort()
    if len(s2) == 0:
        print("None")
    else:
        for m in s2:
            print(m,end=" ")
        print()