#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=NULL;
    newnode->right=NULL;
    return newnode;
}
Node *insert(Node *root,int val){
    if(root==NULL)
        return;
    if(val < root->data)
        root->left=insert(root->left,val);
    else
        root->right=insert(root->right,val);
    return root;
}
Node *levelorder(){
    
}
int main(){
    int n;
    scanf("%d",&n);
    if(n<=0){
        printf("Invalid input");
        return 0;
    }
    for(int i=0;i<n;i++){
        int x;
        scanf("%d",&x);
        if(x<0){
            printf("Invalid input");
        return 0;
        }
        root=insert(root,x);
    }
    levelorder(root);
    return 0;
}