#include <iostream>
#include<bits/stdc++.h>
using namespace std;
string change(string s)
{
int n=s.size();
vector<int> v;
for(int i=0;i<n;i++)
{
if(isdigit(s[i]))
{
v.push_back(s[i]-'0');
}
}
string ans="";
sort(v.begin(),v.end());
int a=v.size();
for(int i=0;i<a;i++)
{
ans.push_back(v[i]+'0');
if(i!=(a-1))
ans.push_back('+');
}
return ans;
}
int main()
{
cout << change("6+3");
return 0;
}
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