program tong_so_chan;
var
  n, tong: integer;
  i: integer;
begin
  write('Nhap so nguyen duong n: ');
  readln(n);

  tong := 0;
  for i := 0 to n do
  begin
    if i mod 2 = 0 then
    begin
      tong := tong + i;
    end;
  end;

  writeln('Tong cac so chan be hon hoac bang ', n, ' la: ', tong);
  readln;
end.