// editor1
#include<stdio.h>
#include<stdlib.h>

typedef struct Node{
    int data;
    struct Node*next;
    struct Node*prev;
}Node;


Node*head=NULL;

Node*createNode(int val){
 Node*n = (Node *)malloc(sizeof(Node));
 n->data=val;
 n->prev=NULL;
 n->next=NULL;
 
 return n;
}
void insertAtEnd(int val){
    Node* newNode=createNode(val);
    if(head==NULL){
        head=newNode;
        return;
    }
    Node*temp=head;
    while(temp->next!=NULL){
    temp+temp->next;
}
temp->nextNode;
newNode->prev=temp;
}

void display(){
    Node* temp=head;
    while(temp!=NULL){
        printf("%d", temp->data);
        temp=temp->next;
    }
}
int main(){
    int n;
    scanf("%d",&n);
    if(n=0){
        printf("Invalid input");
        return 0;
    }
    insertAtEnd(a);
}
display();
return 0;
}