    do i = 0, N     if (c(i) .ne. 0.0) STOP 0   end do    !$acc kernels async (0)   !$acc loop   do i = 0, N     a(i) = 0   end do   !$acc end kernels    !$acc kernels async (0)   !$acc loop   do i = 0, N     b(i) = 0   end do   !$acc end kernels    !$acc kernels wait (0, 0)   !$acc loop   do i = 0, N     c(i) = a(i) + b(i)   end do   !$acc end 