tijei

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