void inter( nodd *&prim)
 {nodd *p=prim,*r,*q,*s;
  while(p->urm)
   {q=p->urm;
    r=p->prec;
    s=q->urm;
    if(r) r->urm=q;
   q->prec=r;
   p->urm=s;
   if(s) s->prec=p;
  p->prec=q;
  q->urm=p;
  if(p==prim) prim=q;
  p=p->urm;
 }
}