s = input().strip()
n = []
factor = []

for ch in s:
    n.append(int(ch))

n.reverse()

for i in range(len(n)):
    flag = True
    for j in range(i):
        if n[j] == n[i]:
            flag = False
    if flag:
        factor.append(n[i])

print("".join(map(str, factor)))      #注意join的用法，直接"".join(factor)会报错