#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  vector<float> coordinates;
  for (int i = 0; i < (int)(n); ++i) {
    float a, b;
    cin >> a >> b;
    coordinates.push_back(a);
    coordinates.push_back(b);
  }
  float sum = 0;
  std::cout << fixed;
  std::cout << setprecision(9);
  for (int i = 0; i < coordinates.size() - 2; i += 2) {
    sum += sqrt(pow(abs(coordinates[i] - coordinates[i + 2]), 2) +
                pow(abs(coordinates[i + 1] - coordinates[i + 3]), 2)) /
           50;
  }
  cout << sum * k << '\n';
}
