#include <bits/stdc++.h>
using namespace std;
pair<int, int> p[101];
int main() {
  int n, k;
  cin >> n >> k;
  double sum = 0.0;
  for (int i = 0; i < n; i++) {
    cin >> p[i].first >> p[i].second;
  }
  for (int i = 0; i < n - 1; i++) {
    sum += sqrt(pow(abs(p[i + 1].first - p[i].first), 2) +
                pow(abs(p[i + 1].second - p[i].second), 2));
  }
  cout << fixed << setprecision(30) << sum * k / 50;
}
