#include <iostream>
#include <cmath>

#include "geometry.hpp"

// import java.util.List;
// import java.util.*;
// import java.awt.*;

// from math import sqrt
// from math import *

using std::cin;
using std::cout;
using std::endl;


/**
 * Reads points in plane from standard input in form
 *
 * 0 0
 * 1 1
 * 3 1
 * 4 0
 *
 * and outputs the total length of the segments that
 * connect them.
 *
 * Compile with
 *
 * g++ -Wall -pedantic -std=c++17 -o Distance distance.cpp
 *
 * and then run with
 *
 * ./Distance
 */
int main(int argc, char **argv)
{
  double last_x, last_y;
  double x, y;
  double total_distance = 0.0;

  cin >> last_x >> last_y; // extract from stream cin (standard input)
  while (cin >> x >> y)
    {
      total_distance += geometry::euclidean_distance(last_x, last_y, x, y);
      last_x = x;
      last_y = y;
    }
  cout << total_distance << endl;
}