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

void process(int array[250] , int length){

    sort(array , array + length);

    for(int i = 0 ; i < length ; i++){

        cout << array[i];

        if(i == length - 1){

            break;

        }

        cout << "+";
    }

}

int main() {

    string series;

    int countPlus = 0;

    int array[250];

    cin >> series;

    int length = series.length();

    if(length <= 100){

        for(int i = 0 ; i < length ; i++){

            if(series.at(i) == '+'){

                countPlus++;

            }

            if(series.at(i) != '+'){

                array[i - countPlus] = series.at(i) - 48;

            }

        }

        int len = length - countPlus;

        process(array , len);

    }else{

        exit(0);

    }
    return 0;
}