public void appendLastN(int n) throws Exception {
int N=this.size();
n=n%N;
Node thead=this.head;
Node prev=this.head;
Node curr=prev.next;
for(int i=0;i<N-n-1;i++){
prev=curr;
curr=curr.next;
}
prev.next=null;
Node temp=curr;
while(temp.next!=null){
temp=temp.next;
}
temp.next=thead;
this.head=curr;
}