#include<stdio.h>
#include<stdlib.h>
typedef struct node
{
    int data;
    struct node *left,*right;
}node;

node* create(int num)
{
    node*newnode=(node*)malloc(sizeof(node));
    newnode->data=num;
    newnode->left=NULL;
    newnode->right=NULL;
    return newnode;
}
node *insert(node* root,int num)
{
    if(root==NULL)
    return create(num);
    if(num<root->data)
    root->left=insert(root->left,num);
    else if(num<root->data)
    root->right=insert(root->right,num);
    return root;
}
void postorder(node* node)
{
    if(root !=NULL)
    {
    postorder(root->left);
    postorder(root->right);
    printf("%d",root->data);
    }
}
int main(){
int size,num;
scanf("%d",&size);
if(size<0)
{
    printf("Invalid input");
    return 0;
}
for(int i=0;i<size;i++)
{
    scanf("%d",&num);
    root=insert(root,num);
    if(n<0)
    {
        printf("Invalid input");
        return 0;
    }
    postorder(root);
    return 0;
}