#include<stdio.h>
#include<stdlib.h>
typedef struct node {
    int data;
    struct node*prev;
    struct node*next;
} Node;
Node *head=NULL, *tail=NULL;
void create (int num){
    Node * newnode=(Node*)malloc(1*sizeof(Node));
    newnode->data = num;
    newnode->next=NULL;
    newnode->prev=NULL;
    if(head=NULL){
        head=newnode;
        tail=newnode;
    }else{
        newnode->prev=tail;
        tail->next=newnode;
        tail=newnode;
    }
}
void display()
Node *itr;
for(itr=headhead;itr!=NULL;itr=itr->next){
    printf("%d",itr->data);
}
}
int main(){
    int size,itr,num;
    scanf("%d",&size);
    if(size<=0){
        printf("Invalid input")
    }
}