// editor2
#include<stdio.h>
#include<stdlib.h>
typedef struct Node{
    int data;
    struct Node *left,*right;
}nd;
nd *root=NULL;
nd *create(int num){
    nd *newnode=(nd*)malloc(sizeof(nd));
    newnode->data=num;
    newnode->left=newnode->right=NULL;
    return newnode;
}
nd *insert(nd *root,int num){
   if(root==NULL)return create(num);
   if(num==root->data)return root;
   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(nd *root){
    if(root!=NULL){
        postorder(root->left);
        postorder(root->right);
        printf("%d",root->data);
    }
}
int main(){
    int n,num;
    nd *root=NULL;
    scanf("%d",&n);
    if(n<0){
        printf("Invalid input");
        return 0;
    }
    for(int i=0;i<n;i++){
        scanf("%d",&num);
        if(val<0){
            printf("Invalid input");
            return 0;
        }
        root=insert(root,num);
    }
    postorder(root);
    return 0;
}