text: #include <bits/stdc++.h>
  #define ll long long
  
  using namespace std;
  
  int main()
  {
      string str;
      cin>>str;
      ll cop[1000];
      ll ln=str.size();
      str+='+';
      ll num=0,j=0;
      for(ll i=0;i<=ln;i++)
      {
          if(str[i]=='+')
          {
              cop[j]=num;
              num=0;
              j++;
          }
          else
          {
              num=num*10+(str[i]-'0');
          }
      }
      //stringstream ss;
  
      sort(cop,cop+j);
      cout<<cop[0];
      for(ll i=1;i<j;i++)
      {
          cout<<'+'<<cop[i];
      }
      cout<<endl;
      return 0;
  }
  