! 愚直パターン
program main
  
  implicit none
  
  integer(8):: n, i, ans, it, keep
  integer:: x(1:200000)
  integer, allocatable:: a(:)
  
  read (*, *) n
  allocate(a(n))
  read (*, *) a(1:n)
  
  do i = 1, n
    x(a(i)) = 1
  end do
  
  ans = n
  do i = 2, 200000
    if (x(i - 1) > 0 .and. x(i) > 0) then
      keep = 1
      do it = i, 199998, 2
        if (x(it + 2) > 0) then
          keep = keep + 1
        else
          exit
        end if
      end do
      ans = ans + keep
    end if
  end do
  
  write (*, '(i0)') ans
  
end program main