#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main() {
	ll n, tmp;
	vector<int> cnt(10);
	vector<int> s;
	vector<int> vis(10);
	cin >> n;
	tmp = n;
	while(tmp > 0) {
		cnt[tmp%10]++;
		s.push_back(tmp%10);
		tmp /= 10;
	}
	reverse(s.begin(), s.end());
	stack<int> st;
	for (int i = 0; i < s.size(); ++i) {
		//cout << s[i] << endl;
		cnt[s[i]]--;
		if (st.empty()) {
			st.push(s[i]);
			vis[s[i]] = 1;
		} else {
			while(!st.empty() && st.top() < s[i] && cnt[st.top()] && !vis[s[i]]) {
				vis[st.top()] = 0;
				st.pop();
			}
			if (!vis[s[i]]) st.push(s[i]), vis[s[i]] = 1;
		}
	}
	ll ans = 0, T = 1;
	while (!st.empty()) {
		ll x = st.top();st.pop();
		ans += x*T;
		T *= 10;
	}
	cout << ans << endl;
	return 0;
}