#include <bits/stdc++.h>
using namespace std;
namespace geometry {
struct point {
  int x, y;
  point() : x(0), y(0) {}
  point(int x_, int y_) : x(x_), y(y_) {}
};
double distance(point l, point r) {
  return sqrt(static_cast<double>(r.x - l.x) * (r.x - l.x) +
              static_cast<double>(r.y - l.y) * (r.y - l.y));
}
void task() {
  int n = 0, k = 0;
  vector<point> v;
  cin >> n >> k;
  point t;
  for (size_t i = 0; i < n; ++i) {
    cin >> t.x >> t.y;
    v.push_back(t);
  }
  const vector<point>::size_type size = v.size();
  double dist = 0.0;
  for (size_t j = 0; j < (size - 1); ++j) {
    dist += distance(v[j], v[j + 1]);
  }
  double time = (dist / 50) * k;
  cout << fixed << setprecision(6) << time << "\n";
}
}  // namespace geometry
int main() {
  geometry::task();
  return 0;
}
