fcn longestSequence(ns){ // based on Patience sorting
   piles:=L();
   backPtr:='wrap(np){ return(np-1,if(np) piles[np-1].len()-1 else -1) }; // maybe (-1,-1)
   foreach n in (ns){ newPile:=True;   // create list of sorted lists
      foreach e,p in (piles.enumerate()){
	 if(n<p[-1][0]){
	    p.del(1,-1)  // only need the first and last elements
	    .append(T(n,backPtr(e))); newPile=False;
	    break;
	 }
      }
      if(newPile) piles.append(L(T(n,backPtr(piles.len()))));
   }
   reg r=L(),p=-1,n=0;
   do{ n,p=piles[p][n]; r.write(n); p,n=p; }while(p!=-1);
   r.reverse()
}