#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
using namespace std;
#define sf scanf
#define pf printf
typedef long long ll;
int a[105];
int main()
{
string s;
int i, k, len;
cin >> s;
len = s.length();
k=1;
int count = 1;
for(i=0; i<len; i++)
{
a[0] = s[0]-'0';
if(s[i]=='+')
{
a[k] = s[i+1]-'0';
k++;
count++;
}
}
sort(a, a+k);
for(k=0; k<count; k++)
{
cout << a[k];
if(k==(count-1))
{
break;
}
cout <<"+";
}
}
#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
using namespace std;
#define sf scanf
#define pf printf
typedef long long ll;
int a[105];
int main()
{
string s;
int i, k, len;
cin >> s;
len = s.length();
k=1;
int count = 1;
for(i=0; i<len; i++)
{
a[0] = s[0]-'0';
if(s[i]=='+')
{
a[k] = s[i+1]-'0';
k++;
count++;
}
}
sort(a, a+k);
for(k=0; k<count; k++)
{
cout << a[k];
if(k==(count-1))
{
break;
}
cout <<"+";
}
}