easy

#include<iostream>
#include<string>
using namespace std;
int main()
{
    string s,s1 = "",s2 = "";
    cin >> s;
    for(int i = 0;i < s.size();i++){if(i % 2 != 0)s1 += s[i];else s2 += s[i];}
    if(s1 > s2)cout << s1 << s2;
    else cout << s2 << s1;
    return 0;
}