// editor1
#include<stdio.h>
#include<stdlib.h>
typedef struct TreeNode{
    int data;
    struct TreeNode* left;
    struct Treenode* right;
}Node;
Node* create(int num){
    Node* newnode=(Node*)malloc(sizeof(Node));
    newnode->data=num;
    newnode->left=newnode->right=NULL;
    return newnode;
}
Node* buildTree(int arr[],int n){
    if(n<=0)return NULL;
    Node* root=create(arr[0]);
    Node* queue[20];
    int front=0,rear=0;
    queue[rear++]=root;
    int i=1;
    while(1<n){
        Node* curr=queue[front++];
        if(i<n){
            curr->left=create(arr[i++]);
            queue[rear++]=curr->left;
        }
        if(i<n){
            curr->right=create(arr[1++]);
            queue[rear++]=curr->right;
        }
    }
    return root;
}
void inorder(Node* root){
    Node* stack[20];
    int top=-1;
    Node* curr=root;
    while(curr || top!=-1){
        while(curr){
            stack[++top]=curr;
            curr=curr->left;
        }
        curr=stack[top--];
        printf("%d",curr->data);
        curr=curr->right;
    }
}
int main(){
    int n,arr[20];
    scanf("%d",&n);
    if(n<=0){
        printf("Invalid input");
        return 0;
    }
    for(int i=0;i<n;i++){
        scanf("%d",&arr[i]);
        if(arr[i]<=0){
            printf("Invalid input");
            return 0;
        }
    }
    Node* root=buildTree(arr,n);
    return 0;
}