n reversekNode(n head,n pre,n frst,int i,int m){
    if(head!=NULL){
        if(i<m-1){
            n nxt = head->next;
            head->next = pre;
            if(i==0)
                frst = head;
            return reversekNode(nxt,head,frst,i+1,m);
        }else{
            n nn = head->next;
            head->next=pre;
            if(head->next!=NULL){
                frst->next = reversekNode(nn,head,NULL,0,m);
            }
            return head;
        }
    }
}

Node *reverseList(Node *a, Node *b)
{
    if (b == NULL)
        return a;

    Node *head = reverseList(b, b->next);
    b->next = a;
    a->next = NULL;
    return head;
}

if (head != NULL)
    head = reverseList(head, head->next);