program energy

 != unit (m) :: height
 != unit (kg) :: mass
 real, parameter :: mass = 3.00, gravity = .81, height = 4.20

 integer :: i = 0
 integer :: j = i
  
 != unit (kg m**2 / s**2) :: potential_energy
 real :: potential_energy
 
 potential_energy = mass * gravity * height
end program energy