// editor5
#include<stdio.h>
#include<stdlib.h>
typedef struct node{
    int data;
    struct node *left;
    struct node *right;
    
}nd;
nd *create(int num){
    nd *newnode=(nd*)malloc(sizeof(nd))
    newnode->data=num;
    newnode->left=NULL;
    newnode->right=NULL;
    return newnode;
}
nd *inserted(nd *root,int num){
    if(root==NULL){
        return create(num);
        
    }
    if(num<root->data)
    root->left=insert(root->left,num);
    else
    root->right=insert(root->right,num);
    return root;
}
void post(nd *root){
    if(root==NULL){
        return;
    }
    post(root->left);
    post(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(num<100 || num>10000){
            printf("Invalid input");
            return 0;
        }
        root=insert(root,num);
    }
    post(root);
    return 0;
}