#include <bits/stdc++.h>
using namespace std;
double distance(double x1, double y1, double x2, double y2) {
  double dx = x2 - x1;
  double dy = y2 - y1;
  return sqrt(dx * dx + dy * dy);
}
int main() {
  ios_base::sync_with_stdio(false);
  int n, k;
  cin >> n >> k;
  vector<int> x(n), y(n);
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
  }
  double d = 0;
  for (int i = 1; i < n; i++) {
    d += distance(x[i - 1], y[i - 1], x[i], y[i]);
  }
  cout << setprecision(12) << d * k / 50 << endl;
}
