#include <iostream>
using namespace std;

int main()
{
	string s;
	cin >> s;

	for (int i = 0; i < s.length() - 1; i++)
	{
		for (int j = i + 1; j < s.length(); j++)
		{
			if (int(s[i]) > int(s[j]))
			{
				char t = s[i];
				s[i] = s[j];
				s[j] = t;
			}
		}
	}
	cout << s;
}