#include <bits/stdc++.h>
#define int long long
using namespace std;
string s;
priority_queue<int>q;
signed main(){
	cin>>s;
	int n=s.size();
	for(int i=0;i<n;i++){
		if(s[i]>='0' && s[i]<='9'){
			q.push(s[i]-'0');
		}
	}
	bool flag=false;
	while(!q.empty()){
		if(q.top()!=0){
			flag=true;
		}
		if(!flag && q.top()==0){
			cout<<0;
			return 0;
		}
		cout<<q.top();
		q.pop();
	}
}