#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
using namespace std;

int main()
{
	string str;
	while (cin >> str)
	{
		int len = str.length();
		vector<int>count(10,0);
		for (int i = 0; i < len; i++)
		{
			count[str[i] - '0']++;
		}
		for (int i = 0; i < str.length()-1; i++)
		{
			if (str[i] <= str[i + 1] && count[str[i] - '0'] > 1)
			{
				count[str[i] - '0']--;
				str.erase(i, 1);
				i--;
			}
		}
		for (int i = str.length() - 1; i >=0; i--)
		{
			if (count[str[i] - '0'] > 1)
			{
				count[str[i] - '0']--;
				str.erase(i, 1);
			}
		}
		cout << str << endl;
	}
	return 0;
}