#include <stdio.h>
#include<stdlib.h>
typedef struct Node{
    int data;
    struct Node *left; 
    struct Node *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(int arr[],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;
    inorder(root->left);
    inorder(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=buildTree(arr,n,0);
    preorder(root);
    printf("\n");
    inorder(root);
    printf("\n");
    postorder(root);
    printf("\n");
    
    return 0;
}