#include <fstream>
#include <iostream>
#define INFINIT 2000000000
using namespace std;

ifstream fin("bilatime.in");
ofstream fout("bilatime.out");

struct nod{
    int info;
    nod * st, * dr;
};

struct elem{
    nod * adr;
    elem * next;
};

void citire(nod * & p)
{
    int x;
    fin >> x;
    if(x == 0)
        p = NULL;
    else
    {
        p = new nod;
        p -> info = x;
        citire(p -> st);
        citire(p -> dr);
    }
}

void Adauga(nod * ce, elem * & ultim)
{
    elem * aux = new elem;
    aux -> adr = ce;
    aux -> next = NULL;
    ultim -> next = aux;
    ultim = aux;
}

void Elimina(elem * & prim)
{
    elem * aux = prim;
    prim = prim -> next;
    delete aux;
}

void BFS(nod * p)
{
    elem * prim, * ultim;
    prim  = new elem;
    ultim = prim;
    prim -> next = NULL;
    prim -> adr = p;
    while(prim != NULL)
    {
        nod * aux = prim -> adr;
        fout << aux -> info << " ";
        if(aux -> st != NULL)
            Adauga(aux -> st , ultim);
        if(aux -> dr != NULL)
            Adauga(aux -> dr , ultim);
        Elimina(prim);
    }
}

void stergeTot(nod * & p)
{
    if(p != NULL)
    {
        stergeTot(p -> st);
        stergeTot(p -> dr);
        delete p;
        p = NULL;
    }
}

int main()
{
    nod * p = NULL;
    citire(p);
    BFS(p);
    stergeTot(p);
    return 0;
}