{ tde }

program Discount;

{$APPTYPE CONSOLE}
{ Delphi }

(*
 * Problem  :   DISCOUNT
 * Contest  :   UOI-2008 (LVIV)
 * Type     :   Solution
 * Date     :   March 18, 2008
 * Version  :   1.0
 * Author   :   Shamil Yagiyayev
 * Language :   Delphi
 * Compiler :   Turbo Delphi 2006
 * Link     :
 * Algorithm:   Author Solution
 *)

const
  MAX_N = 10000;
var
  n, i, sum : integer;
  A : array[1..MAX_N] of integer;

procedure swap(var a : integer; var b : integer);
var c : integer;
begin
  c:=a;
  a:=b;
  b:=c;
end;

procedure rebuild(f, l: integer);
var k : integer;
begin
  while 2*f+1 <= l do
  begin
    if A[2*f] < A[2*f+1] then k:=2*f else k:=2*f+1;
    if A[f] > A[k] then
    begin
      swap(A[f], A[k]);
      f := k;
    end
    else break;
  end;
  if (2*f = l) and (A[f] > A[l]) then swap(A[f], A[l]);
end;

procedure heapSort;
var i : integer;
begin
  for i:=(n div 2) downto 1 do
    rebuild(i, n);

  for i:=n downto 2 do
  begin
    swap(A[1], A[i]);
    rebuild(1, i-1);
  end;
end;

begin
  Assign(input, 'discount.dat');
  Reset(input);
  ReadLn(n);
  for i:=1 to n do
    Read(A[i]);
  Close(input);

  heapSort;

  sum := 0;
  for i := 1 to n do
    if i mod 3 <> 0 then sum := sum + a[i];

  Assign(output, 'discount.sol');
  Rewrite(output);
  Writeln(sum);
  Close(output);
end.