Count, Total Even numbers

CREATE PROC sp_TongIn
  @n int,
  @count int out,
  @total int out
AS
  DECLARE @last int
  DECLARE @first int
  SET @first = 2 -- so chan dau tien

  IF (@n % 2 = 0) SET @last = @n
  ELSE SET @last = @n - 1

  SET @count = @last / 2

  SET @total = (@count / 2) * (@last + @first) -- e.g.: 2 4 6 8 10 => (2 + 10) + (4 + 8) = 12 * 2
  IF (@count % 2 <> 0)
  BEGIN
    DECLARE @middle int
    SET @middle = @last / 2 + ((@last % 2 + 1) % 2) -- e.g.: 10 / 2 + ((10 % 2 + 1) % 2) = 5 + 1 = 6
    SET @total = @total + @middle
  END
GO

DECLARE @count int
DECLARE @total int

EXEC sp_TongIn 10, @count out, @total out
PRINT 'So luong so chan: ' + CAST(@count as VARCHAR)
PRINT 'Tong so chan:' + CAST(@total as VARCHAR)