#include <bits/stdc++.h>
using namespace std;
int main(int argc, char const* argv[]) {
  double spd = 50.0;
  int n, k;
  cin >> n;
  cin >> k;
  double dist = 0.0;
  double x1, y1, x2, y2;
  dist = 0.0;
  cin >> x1 >> y1;
  for (unsigned int i = 0; i < n - 1; i += 1) {
    cin >> x2 >> y2;
    dist = dist + sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
    x1 = x2;
    y1 = y2;
  }
  cout << fixed << setprecision(9) << dist * (double)(k) / spd << endl;
  return 0;
}
