#include <iostream>
#include <string>
#include <unordered_map>  
using namespace std;

int main() {
  unordered_map<char, int> cnt;
  cnt['9'] = 0;
  cnt['8'] = 0;
  cnt['7'] = 0;
  cnt['6'] = 0;
  cnt['5'] = 0;
  cnt['4'] = 0;
  cnt['3'] = 0;
  cnt['2'] = 0;
  cnt['1'] = 0;
  cnt['0'] = 0;
  
  string n;
  cin >> n;

  for (auto itr = cnt.begin(); itr != cnt.end(); ++itr) {
    for (int j = 0, size = n.size(); j < size; ++j) {
      if (itr->first == n[j]) itr->second++;
    }
  }
  for (auto itr = cnt.begin(); itr != cnt.end(); ++itr) {
    for (int j = 0; j < itr->second; ++j) {
      cout << itr->first;
    }
  }
  return 0;
}