#include <iostream>


using namespace std;

int main()
{
    int temp;
    const int size = 30;
    char str[size];
    for (int i = 0; i < size; i++) {
        cin >> str[i];
    }
    for (int i = 0; i < size; i++) {
        for (int j = i+1; j < size - 1; j++) {
            if (str[i] > str[j])
            {
                temp = str[i];
                str[i] = str[j];
                str[j] = temp;
            }
        }
    }
    cout << endl;
    for (int i = 0; i < size; i++) {
        cout << str[i];
    }
}