#include <iostream>
using namespace std;

//---------------------------------------------------------------------

class link1
{
  private:
   int element;
   link1 *left, *right;
  public:
   link1(int val)//constructer
   {
    right=NULL;
    left=NULL;
    element=val;
   };
   
   ~link1()//destructer
   {
    if (right) delete right;
    if (left) delete left;
   };
    
    void Add(int v)//adding element
   {
    if (v<element)
    {
     if (left) 
      left->Add(v);
     else
      left=new link1(v);
    }
    else
    {
     if (right)
      right->Add(v);
     else
      right=new link1(v);
    }
   };
    
    void Print_elem()//printing element
   {
    if (left) left->Print_elem();
    cout<<element<<" ";
    if (right) right->Print_elem();
   };
};

//---------------------------------------------------------------------

class Tree
{
  private:
   link1 *root;
  public:
   Tree() {root=NULL;}//constructer
  ~Tree() {delete root;}//destructer

   void Print_all()//printing tree
   {
    root->Print_elem();
    cout<<"\n";
   };

   void AddEl(int i)//adding element to tree
   {
    if (!root)
     {
     root=new link1(i);
     }
    else root->Add(i);
   };
};

//---------------------------------------------------------------------

int main(void)
{
 Tree *T;
 int l;
 T= new Tree();
 while (l>=0) 
  {
   cin>>l;
   T->AddEl(l);
  }
 T->Print_all();
 delete T;
 return 0;
}