#include<stdio.h>
#include<stdlib.h>
struck Node
{
 int data;
 struct Node *prev,*next;
};
 int main()
{
 int n, x;
 if(scanf("%d", &n) !=1 || n <= 0)
{
 printf("Invalid Input");
 return 0;
}
 struct Node *head = NULL, *tail = NULL, *newNode;
 for (int i = 0; i < n; i++)
{
 printf("Invalid Input");
return 0;
}
 newNode = (struct Node*)malloc(sizeof(struct Node));
 newNode->data = x;
 newNode->next = NULL;
 newNode->prev = tail;
 if (tail) tail->next = newNode;
 else head = newNode;
 tail = newNode;
}
 while (head) 
{
 printf("%d", head->data);
 head = head->next;
}
return 0;
}