def check(x, y):
    lx = list(x)
    ly = list(y)
    lx.sort()
    ly.sort()
    if len(lx) != len(ly): return 0
    for i in range(len(lx)):
        if lx[i] != ly[i]: return 0
    return 1
while 1:
    nope = 1
    n = eval(input())
    if n == 0: break
    a = list(input().split())
    p = []
    for i in range(n):
        flag = 1
        for j in range(n):
            if i != j and check(a[i], a[j]) == 1:
                flag = 0
                break
        if flag == 1:
            p.append(a[i])
    if len(p) == 0: print("None",end = " ")
    else :
            p.sort()
            for i in range(len(p)):print(p[i], end = " ")
    print()