#include <iostream>
#include <unordered_set>
using namespace std;
int main()
{
    string s;
    cin >> s;
    unordered_set<char> se;
    for (int i = s.size()-1; i != -1; i--) {
        if (se.find(s[i]) == se.end()) {
            cout << s[i];
            se.emplace(s[i]);
        }
    }
}