struct node
              {
                  int date;
                  node *lc;
                  node *rc;
              };      
              
              
              void vin(int k)
             {
                  node *t=new node;
                  t->date = k;
                  t->lc=NULL;
                  t->rc=NULL;            
                  if(start == NULL)
                  {
                          start=t;
                  }
                  else if(start->date < k)
                  {    
                       if(start->rc==NULL)
                                          start->rc=t;
                       else
                       {                   
                             start = start->rc;
                             vin(k);
                       }
                  }
                  else
                  {  
                       if(start->lc==NULL)
                                          start->lc=t;
                        else
                        {                       
                                                start = start->lc;
                                                vin(k);
                        }
                  }
             }