// 不知道满不满足要求

#include <iostream>
#include <vector>
#include <string>
#include <cstring>
using namespace std;
int main() {
	string str;
	while (cin >> str) {
		vector<char> vec;
		for (char ch : str) {
			int index = -1;
			for (int i = 0; i < vec.size(); ++i) {
				if (vec[i] == ch) {
					index = i;
					break;
				}
			}
			if (index == -1) {
				vec.push_back(ch);
			}
			else if (index != vec.size() - 1 && vec[index] < vec[index + 1]) {
				continue;
			}
			else {
				while (index < vec.size() - 1) {
					vec[index] = vec[index + 1];
					++index;
				}
				vec[index] = ch;
			}
		}
		for (char ch : vec) {
			cout << ch;
		}
		cout << endl;
	}
	return 0;
}