#include <boost/units/quantity.hpp>
#include <boost/units/systems/si.hpp>
#include <boost/units/io.hpp>
#include <boost/units/systems/si/codata_constants.hpp>
#include <boost/math/constants/constants.hpp>

using namespace boost::units;
using namespace boost::units::si::constants::codata;
using namespace boost::math::constants;

int main()
{
  quantity<si::electric_charge> q = 100 * si::coulombs;
  quantity<si::electric_potential> u = 100 * si::volts;
  quantity<si::length> r = 1 * si::metres;


  quantity<si::dimensionless> epsilon_r = 1;

  quantity<si::electric_potential> phi = (1./4/M_PI) / epsilon_r / epsilon_0 * q/r;

  quantity<si::capacitance> c = q/u;
  std::cout << c << std::endl;
}