#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  vector<pair<double, double>> v;
  double x, y;
  int n, k;
  pair<double, double> temp = make_pair(0, 0);
  cin >> n >> k;
  for (int i = 0; i < n; i++) {
    cin >> x >> y;
    v.push_back(make_pair(x, y));
  }
  temp = v[0];
  double ans = 0;
  for (int i = 1; i < n; i++) {
    ans =
        ans +
        abs(sqrt(((v[i].first - temp.first) * (v[i].first - temp.first)) +
                 ((v[i].second - temp.second) * (v[i].second - temp.second))));
    temp = v[i];
  }
  ans = (ans * 1 / 50) * k;
  printf("%.9f", ans);
  return 0;
}
