void push_queue(struct Node* tail, int val){

	if(tail==head){
		struct Node* cur = (struct Node*)malloc(sizeof(struct Node));
		cur->val=val;
		cur->next =NULL;
		tail=cur;
		head->next = tail;
	}
	if(tail==NULL){
		head->val = tail->val = val;
		head->next = tail->next = NULL;
	}
	struct Node* cur = (struct Node*)malloc(sizeof(struct Node));
	cur->next = NULL;
	cur->val = val;
	tail->next=cur;
	tail = cur;
}

struct Node* pop_queue(struct Node* head, int val){
	Node* cur = head;
	if(head==NULL){
		cout << "queue is empty" << endl;
		return 0;
	}
	head=head->next;
	return cur;
}