#include <stdio.h>
#include <stdlib.h>
typedef struct tree{
    int data;
    struct tree *left;
    struct tree *right;
}nd;
nd *create(int val){
    nd *newnode=(nd*)malloc(sizeof(nd));
    newnode->data=val;
    newnode->left=NULL;
    newnode->right=NULL;
    return newnode;
}
nd *insertBTlvlor(int a[],int n){
    if(n==0||a[0]==0){
        return NULL;
    }
    nd *q[100];
    int front=0;rear=0;
    nd *root=create(a[0]);
    q[rear++]=root;
    int i=1;
    while(i<n &&front<rear){
        nd *curr=q[front++];
        if(i<n&&a[i]!=0){
            curr->left=create(a[i]);
            q[rear++]=curr->left;
        }
        i++;
        if(i<n&&a[i]!=0){
            curr->right=create(a[i]);
            q[rear++]=curr->right;
        }
        i++;
    }
    return root;
}
void in(nd *root){
    if(root==NULL){
        return;
    }
    in(root->left);
    printf("%d ",root->data);
    in(root->right);
}
void pre(nd *root){
    if(root==NULL){
        return;
    }
    printf("%d ",root->data);
    pre(root->left);
    pre(root->right);
}
void po(nd *root){
    if(root==NULL){
        return;
    }
    po(root->left);
    po(root->right);
    printf("%d ",root->data);
}
int main(){
    int n;
    scanf("%d",&n);
    if(n<0||n>100){
        printf("Invalid input");
    }
    int a[100];
    nd *root=NULL;
    for(int i=0;i<n;i++){
        scanf("%d",&a[i]);
        if(a[i]<0){
            printf("Invalid input");
            return 0;
        }
    }
    root=insertBTlvlor(a,n);
    pre(root);
    printf("\n");
    in(root);
    printf("\n");
    po(root);
    return 0;
}