#include<iostream>
#include <string.h>
using namespace std;
typedef struct BiTNode
{
char data;
struct BiTNode *lchild,*rchild;
}BiTNode,*BiTree;
void CreateBiTree(BiTree &T,char S[],int &i)
{//先序建立二叉树
if(S[i]=='0')
T=NULL;
else
{
T=new BiTNode;
T->data=S[i];
CreateBiTree(T->lchild,S,++i);
CreateBiTree(T->rchild,S,++i);
}
}
void DoubleTraverse(BiTree T)
{//双序遍历二叉树T的递归算法
/**************begin************/
/**************end************/
}
int main()
{
char S[100];
while(cin>>S)
{
if(strcmp(S,"0")==0) break;
int i=-1;
BiTree T;
CreateBiTree(T,S,++i);
DoubleTraverse(T);
cout<<endl;
}
return 0;
}