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

int main() {
    string s;
    cin >> s;
    
    // 提取所有数字字符
    string d = "";
    for (char c : s) {
        if (c >= '0' && c <= '9') {
            d += c;
        }
    }
    
    // 按从大到小排序
    sort(d.begin(), d.end(), greater<char>());
    
    // 输出结果
    cout << d << endl;
    
    return 0;
}