#include <stdio.h>
#include <stdlib.h>

typedef struct node{
    int  data;
    struct node *left;
    struct node *right;
}Node;

Node *root=NULL;
Node *create(int val){
    Node *newnode=(Node*)malloc(sizeof(Node));
    newnode->data=val;
    newnode->left=newnode->right=NULL;
    return newnode;
}

Node *insertBTS(Node *root, int t){
    if(root==NULL){
        return create(t);
    }
    
    if(t<root->data){
        root->left=insertBTS(root->left, t);
    }
    else
        root->right=insertBTS(root->right), t);
    return root;
}

void postorder(Node *root){
    if(root==NULL){
        return;
    }
    
    postorder(root->left);
    postorder(root->right);
    printf("%d", root->data);
    
}


int main(){
    int size;
    scanf("%d", &size);
    if(size<0){
        printf("invalid input");
        return 0;
    }
    Node *root=NULL;
    for(int i=0; i<size; i++){
        int time;
        scanf("%d", &time);
        if(time<5){
            printf("Invalid input");
            return 0;
        }
        root=insertBTS(root, time);
    }
    postorder(root);
}