#include<stdio.h>
#include<string.h>
#include<stdlib.h>
typedef struct TNode{
int v;
struct TNode *left, *right;
}Node;//建立节点
Node *Buildtree(Node * root, int n){
if(root == NULL){
root = (Node*)malloc(sizeof(Node));
root -> v = n;
root -> left = root -> right = NULL;
return root;
}
if(root -> v > n )
root -> left = Buildtree(root -> left, n);
else
root -> right = Buildtree(root -> right, n);
return root;//每次返回头指针，才能进行下一次的比较
}//建树
void DLR(Node *root, int n)//前序遍历
{
if(n != 1)
printf(" %d", root -> v);
else
printf("%d", root -> v);
if(root -> left != NULL)
DLR(root -> left, 2);
if(root -> right != NULL)
DLR(root -> right, 2);
}
int main(){
int n, m, i;
Node * root = NULL;
while(scanf("%d", &n) != EOF){
for(i = 0;i < n; i++)
{
scanf("%d", &m);
root = Buildtree(root, m);
}
DLR(root, 1);
printf("\n");
}
return 0;
}