#include<cstdio>
#include<iostream>
#include<algorithm>
#include<string>
using namespace std;

int main(){
	int n,m;
	string s;
	cin>>s;
	n=s.length();
	sort(s.begin(),s.end());
	
	for(int i=0;i<n;i++){
		cout<<s[i];
	}
	
}