#include <bits/stdc++.h>
using namespace std;
void init() { return; }
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  init();
  int n, k;
  cin >> n >> k;
  double x[n], y[n];
  double ans = 0;
  double speed = 50.0;
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
    if (i >= 1) {
      double dist =
          sqrtl(pow(abs(x[i] - x[i - 1]), 2) + pow(abs(y[i] - y[i - 1]), 2));
      ans += dist / speed;
    }
  }
  ans = ans * k;
  cout << fixed << setprecision(8) << ans << endl;
  return 0;
}
