// editor1
#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 *build(int a[],int n,int i){
    if(i>=n || a[i]==0)
    return NULL;
    nd *root=ceate(a[i]);
    root->left=build(a,n,2*i+1);
       root->right=build(a,n,2*i+2);
       return root;
}
void in(nd *root){
    if(root==NULL){
        return 0;
    }
    in(root->left);
    printf("%d",root->data);
    in(root->right);
}
int main(){
    int n;
    
    scanf("%d",&n);
    if(n<=0){
        printf("Invalid input");
        return 0;
    }
    int a[n];
    for(int i=0;i<n;i++){
        scanf("%d",&a[i]);
    }
    nd *root=build(a,n,o);
    in(root);
    return 0;
}