function add var PNode integer level integer integer var rest vtmp int

function add(var r: PNode; v: integer; level: integer = 0): integer;
var
  rest, vtmp: integer;
  q, pa, pb, pc: PNode;
begin
  if r = nil then begin
    new(r);
    r^.left := nil;
    r^.right := nil;
    r^.v := v;
    add := random(level div 2);
    exit;
  end;
  if v = r^.v then begin
    add := 0;
    exit;
  end;
  if v < r^.v then begin
    rest := add(r^.left, v, level + 1);
    if rest > 0 then begin
      //левое вращение
     q := r^.left;
     pa := q^.left;
     pb := q^.right;
     pc := r^.right;
     vtmp := r^.v; r^.v := q^.v; q^.v := vtmp;
     r^.left := pa;     
     r^.right := q;
     q^.left := pb;
     q^.right := pc;
    end;
    add := rest - 1;
  end else begin
    rest := add(r^.right, v, level + 1);
    if rest > 0 then begin
      //правое вращение
     q := r^.right;
     vtmp := r^.v; r^.v := q^.v; q^.v := vtmp;
     pa := r^.left;
     pb := q^.left;
     pc := q^.right;
     vtmp := r^.v; r^.v := q^.v; q^.v := vtmp;
     r^.left := q;
     q^.left := pa;
     q^.right := pb;
     r^.right := pc;
    end;
    add := rest - 1;    
  end;
end;