#include <algorithm>
#include <cmath>
#include <fstream>
#include <iostream>
#include <iterator>
#include <numeric>
#include <sstream>
#include <vector>

int main()
{
    std::ifstream ifs { "WAYPOINTS.txt" };
    std::vector<std::pair<double, double>> waypoints { };
    std::transform(std::istream_iterator<std::string>{ ifs },
                   std::istream_iterator<std::string>{ },
                   std::back_inserter(waypoints),
                   [](std::string const& waypoint)
                   {
                       double x, y;
                       std::istringstream iss { waypoint };
                       iss >> x;
                       iss.ignore(1); // ignore -
                       iss >> y;
                       return std::make_pair(x, y);
                   });

    std::adjacent_difference(waypoints.begin(), waypoints.end(),
                             waypoints.begin(),
                             [](std::pair<double, double> const& lhs,
                                std::pair<double, double> const& rhs)
                             {
                                 return std::make_pair(lhs.first - rhs.first,
                                                       lhs.second - rhs.second);
                             });

    std::vector<double> distances(waypoints.size() - 1);
    std::transform(std::next(waypoints.begin()), waypoints.end(), distances.begin(),
                   [](std::pair<double, double> const& diff)
                   {
                       return std::sqrt(diff.first*diff.first + diff.second*diff.second);
                   });

    std::cout << std::accumulate(distances.begin(), distances.end(), 0.0) << std::endl;
}