#include <iostream>
#include <string>
 
int main()
{
	std::string str;
	std::cin >> str;
 
	char tmp;
 
	int i,j;
	for(i=0;i<str.size()-1;++i) {
		for(j = i+1;j<str.size();++j) {
			if(str[i] < str[j])
			{
				tmp = str[i];
				str[i] = str[j];
				str[j] = tmp;
			}
		}
	}
 
	std::cout << str;
 
	return 0;
}