#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  pair<double, double> a[n];
  for (int i = 0; i < n; i++) {
    cin >> a[i].first >> a[i].second;
  }
  double cnt = 0;
  for (int i = 1; i < n; i++) {
    double x =
        sqrt((a[i].second - a[i - 1].second) * (a[i].second - a[i - 1].second) +
             (a[i].first - a[i - 1].first) * (a[i].first - a[i - 1].first));
    cnt += x;
  }
  cout << fixed << setprecision(6) << (cnt * k) / 50.0;
  return 0;
}
