program saxpy
  use, intrinsic :: iso_fortran_env
  
  implicit none
  integer, parameter :: sp = REAL32
  integer, parameter :: dp = REAL64
  integer, parameter :: i64 = INT64
  integer(i64) :: i, n, rate, system_start, system_end
  real(dp),dimension(:),allocatable :: x, y
  real(dp) :: a,cpu_start, cpu_end
  CHARACTER(100) :: my_arg
  
  CALL GET_COMMAND_ARGUMENT(1, my_arg)
  READ(my_arg,*)n

  allocate(x(n),y(n))
  x = 1.0d0
  y = 2.0d0
  a = 2.0d0
  
  CALL system_clock(count_rate=rate)
  call cpu_time(cpu_start)
  call SYSTEM_CLOCK(system_start)
  do i = 1, n
     y(i) = y(i) + a * x(i)
  end do
  call cpu_time(cpu_end)
  call SYSTEM_CLOCK(system_end)
  deallocate(x,y)
  
  print '(a,f8.6)', 'CPU Time: ', cpu_end - cpu_start
  print '(a,f8.6)', 'Wall Time: ', real(system_end-system_start)/real(rate)
  
end program saxpy