#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(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;
    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 = buildTree(arr, n, 0);
    preorder(root);
    printf("\n");
    inorder(root);
    printf("\n");
    postorder(root);
    printf("\n");
    return
}