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

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

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