1 #include <fstream>
 2 #include <iostream>
 3 
 4 using namespace std;
 5 
 6 typedef struct Node{
 7     Node *lch,*rch,*nex;
 8     int x;
 9     Node(int x){
10         this->x=x;
11         lch=NULL;
12         rch=NULL;
13     }
14 }inode;
15 
16 int n,tn;
17 inode *head;
18 
19 void insert(int t);
20 void preOrder(inode *p);
21 
22 int main()
23 {
24     //freopen("D:\\input.in","r",stdin);
25     //freopen("D:\\output.out","w",stdout);
26     int t;
27     while(~scanf("%d",&n)){
28         scanf("%d",&t);
29         head=new inode(t);
30         for(int i=1;i<n;i++){
31             scanf("%d",&t);
32             insert(t);
33         }
34         tn=0;
35         preOrder(head);
36     }
37     return 0;
38 }
39 void insert(int t){
40     inode *p=head,*s=new inode(t);
41     while(p!=NULL){
42         if(t<p->x)
43             if(p->lch!=NULL)    p=p->lch;
44             else{
45                 p->lch=s;
46                 break;
47             }
48         else
49             if(p->rch!=NULL)    p=p->rch;
50             else{
51                 p->rch=s;
52                 break;
53             }
54     }
55 }
56 void preOrder(inode *p){
57     if(p!=NULL){
58         printf("%d",p->x);
59         if(++tn<n)  printf(" ");
60         else    printf("\n");
61         preOrder(p->lch);
62         preOrder(p->rch);
63         delete p;
64     }
65 }