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

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

Node *root = NULL;

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

Node* build(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(i<n){
        Node* curr = queue[front++];
        if(i<n){
            curr->left = create(arr[i++]);
            queue[rear++] = curr->left;
        }
        if(i<n){
            curr->right = create(arr[i++]);
            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(num<0){
            printf("Invalid input");
            return 0;
        }
    }
    Node* root = build(arr, n);
    inorder(root);
    return 0;
}