// editor1
#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 *buildTree(int arr[],int n,int i){
    if(i>=n)
    return NULL;
    Node *root=create(arr[i]);
    root->left=buildTree(arr,n,2*i+1);
    root->right=buildTree(arr,n,2*i+2);
    return root;
}
void inorder(Node *root){
    Node *stact[100];
    int top=-1;
    Node *curr=root;
    
    while(curr!=NULL || top>=0){
    while(curr!=NULL){
        stack[++top]=curr;
        curr=curr->left;
    }
    curr=stack[top--];
    printf("%d",curr->data);
    curr=curr->right;
}
}
int main(){
    int n;
    scanf("%d",&n);
    if(n<=0){
        printf("Invalid input");
        return 0;
    }
    int arr[100];
    for(int i=0;i<n;i++){
        scanf("%d",&arr[i]);
        
    }
    root=buildTree(arr,n,0);
    inorder(root);
    return 0;
}