/*****************************
 Name         : Yoshitak
 Create Date  : 2015/06/05
 Program Name : main.d
 Problem No.  : 256
*****************************/

/*---------------------
 import
-----------------------*/
import std.stdio;
import std.string;
import std.conv;
import std.array;

/*---------------------
 main
-----------------------*/
int main(string[] args)
{
	//input
	uint[] num;
	string input;
	input = chomp(readln());
	
	//into the arry
	num.length = input.length;
	foreach(int i, char c; input){
		num[i] = to!int(c);
	}

  num.sort;
  
	//output
	foreach_reverse(int c; num){
		write(to!char(c));
	}

	return 0;
}