int getNthFromLast(Node *head, int n)
{
       // Your code here
       Node* front = head; 
       while(front && n--)front = front->next;
       if(n>0)
        return -1;
       Node* rear = head;
       while(front){
           front = front->next;
           rear = rear->next;
       }
       return rear->data;
}