#include <bits/stdc++.h>
double cor(int x1, int y1, int x2, int y2) {
  return sqrt(pow((x1 - x2), 2) + pow((y1 - y2), 2)) / 50;
}
int main() {
  double time;
  double num, k, dis = 0, a, b, a1, b1;
  std::cin >> num >> k;
  std::cin >> a1 >> b1;
  std::cout << std::fixed << std::setprecision(9);
  for (int x = 1; x < num; x++) {
    std::cin >> a >> b;
    double m = cor(a1, b1, a, b);
    dis += m;
    a1 = a, b1 = b;
  }
  time = dis * k;
  std::cout << time;
}
