Codeforces 339A

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

#define maxSize 105

int main()
{
	string exp;
	int digit[maxSize];
	int length,index;
	while(cin>>exp)
	{
		length=exp.size();
		index=0;
		for(int i=0; i<length; i+=2)
			digit[index++]=exp[i]-'0';
		sort(digit,digit+index);
		cout<<digit[0];
		if(index>1)
		{
			for(int i=1; i<index; ++i)
				cout<<'+'<<digit[i];
		}
		cout<<endl;
	}
	return 0;
}