#include <bits/stdc++.h>
using namespace std;
bool binsearch(int ar[], int n, int x) {
  int i = 0, j = n - 1;
  while (i <= j) {
    int mid = (i + j) / 2;
    if (ar[mid] < x)
      i = mid + 1;
    else
      j = mid - 1;
  }
  if (i < n)
    return (ar[i] >= x);
  else
    return false;
}
double calculate_dist(int x1, int y1, int x2, int y2) {
  return pow((pow(x2 - x1, 2) + pow(y2 - y1, 2)), 0.5);
}
int main() {
  int n, k;
  cin >> n >> k;
  vector<pair<int, int>> res;
  for (int i = 0; i < n; i++) {
    int a, b;
    cin >> a >> b;
    res.push_back(make_pair(a, b));
  }
  double total_dist = 0;
  for (int i = 0; i < res.size() - 1; i++) {
    double temp = calculate_dist(res[i].first, res[i].second, res[i + 1].first,
                                 res[i + 1].second);
    total_dist += temp;
  }
  printf("%.9f", (total_dist * k) / 50);
  return 0;
}
