#include <bits/stdc++.h>
using namespace std;
template <typename T>
istream& operator>>(istream& in, vector<T>& v) {
  for (auto& it : v) {
    in >> it;
  }
  return in;
}
template <typename T>
ostream& operator<<(ostream& out, vector<T>& v) {
  if (!v.empty()) {
    out << v.front();
    for (int i = 1; i < v.size(); ++i) {
      out << " " << v[i];
    }
  }
  return out;
}
void solve() {
  int n, k, x1, y1, x2, y2;
  double l = 0;
  cin >> n >> k;
  cin >> x1 >> y1;
  for (int i = 0; i < n - 1; ++i) {
    cin >> x2 >> y2;
    l += sqrt(pow((x2 - x1), 2) + pow((y2 - y1), 2));
    x1 = x2, y1 = y2;
  }
  cout << setprecision(7) << l * k / 50;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  solve();
}
