题解 | #提取不重复的整数#

n = input()
reverse_n = n[::-1]
if len(reverse_n) == 1:
    print(reverse_n)
else:
    newlist = []
    newlist1 = []
    for i in reverse_n:
        newlist.append(i)
    for j in range(len(newlist)):
        for m in range(j + 1, len(newlist)):
            if newlist[m] == newlist[j]:
                newlist[m] = ' '
    for ele in range(len(newlist)):
        if newlist[ele] != ' ':
            newlist1.append(newlist[ele])
    print(''.join(map(str, newlist1)))