#include<iostream>
#include<algorithm>
#include<string.h>
using namespace std;
int main(void)
{
	int i, len;
	char n[1000010];
	
	cin >> n;
	len = strlen(n);
	sort(n, n + len);
	for (i = len - 1; i >= 0; i--)
		cout << n[i];
	cout << endl;
	return 0;
}