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

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

Node* createNode(int data){
    if(data==0) return NULL;
    Node* newnode= (Node*)malloc(sizeof(Node));
    newnode->data=data;
    newnode->left=newnode->right=NULL;
    return newnode;
}
Node* buildTree(arr[i],int n, int i){
    if(i>=n||arr[i]==0)
    return NULL;
    
    Node*root=createNode(arr[i]);
    root->left=buildTree(arr,n,2*i+1);
    root->right=buildTree(arr,n,2*i+2);
    return root;
}
void preorder(Node* root){
    if(root==NULL)return;
    printf("%d", root->data);
    preorder(root->left);
    preorder(root->right);
}
void inorder(Node* root){
    if(root==NULL)return;
    inorder(root->left);
    printf("%d", root-> data);
    inorder(root->right);
}
void postorder(Node* root){
    if(root==NULL)return ;
    postorder(root->left);
    postorder(root->right);
    printf("%d", root->data);
}

int main(){
    int n;
    scanf("%d", &n);
    if(n<=0){
        printf("Invalid input");
    }
    int arr[n];
    for(int i=0; i<n ;i++)
    scanf("%d", &arr[i]);
    Node* root=insertbuildTree(arr,0,n);
    preorder(root);
    printf(" ");
    inorder(root);
    printf(" ");
    postorder(root);
    printf(" ");
    return 0;
}