#include <stdio.h>

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

Node *root=NULL;

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


Node* build(int arr[], int val, int i){
    if(i>=val || arr[i]==0){
        return NULL;
    }
    
    Node *root=create(val);
    root->left=build(root->left, val, 2*i+1);
    root->right=build(root->right, val, 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");
        return 0;
    }
    
    int arr[n];
    for(int i=0; i<n; i++){
        scanf("%d", &arr[i]);
    }
    preorder(root);
    printf("\n");
    inorder(root);
    printf("\n");
    postorder(root);
    printf("\n");
    
}