#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  vector<pair<double, double> > v;
  while (n--) {
    double x, y;
    cin >> x >> y;
    v.push_back(make_pair(x, y));
  }
  double res = 0.0;
  double d = 0;
  for (int i = 0; i < v.size() - 1; i++) {
    d += sqrt(
        ((v[i + 1].first - v[i].first) * (v[i + 1].first - v[i].first)) +
        ((v[i + 1].second - v[i].second) * (v[i + 1].second - v[i].second)));
  }
  res = d / 50;
  res *= k;
  printf("%0.9lf\n", res);
}
