// editor1
#include<stdio.h>
#include<stdlib.h>
typedef struct treenode{
    int data;
    struct treenode *left;
    struct treenode *right;
}node;
node* create(int num){
    node* newnode=(node*)malloc(sizeof(node));
    newnode->data = num;
    newnode->left=newnode->right=NULL;
    return newnode;
}
node* buildtree(int arr[],int n){
    if(n<=0)return NULL;
    node* root=create(arr[0])
    node* queue[20];
    int front = 0,rear = 0;
    queue[rear++]=root;
    int i=1;
    while(1<n){
        node* curr = queue[front++];
        if(i<n){
            curr->left=create(arr[i++]);
            queue[rear++]=curr->right;
        }
    }
    return root;
}

void inorder(node* root){
    node* stack[20];
    int top = -1;
    node* curr=root;
    while(curr || top != -1){
        while(curr){
            stack[++top] = curr;
            curr = curr->left;
        }
        curr=stack[top--];
        printf("%d ",curr->data);
        curr = curr->right;
    }
}
int main(){
    int n,arr[20];
    scanf("%d",&n);
    if(n<=0){
        printf("Invalid input");
        return 0;
    }
    for(int i = 0;i<n;i++){
        scanf("%d",&arr[i]);
        if(arr[i]<=0){
            printf("Invalid input");
            return 0;
        }
    }
    node* root = buildtree(arr,n);
    inorder(root);
    return 0;
    }