#include <bits/stdc++.h>
using namespace std;
const int MAX = 1e5 + 10;
long long min(long long a, long long b) {
  if (a > b) return b;
  return a;
}
long long max(long long a, long long b) {
  if (a > b) return a;
  return b;
}
double distance(double x1, double y1, double x2, double y2) {
  return sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n, k;
  cin >> n >> k;
  double xx, yy;
  cin >> xx >> yy;
  double dis = 0;
  for (int i = 0; i < n - 1; i += 1) {
    double x, y;
    cin >> x >> y;
    dis += distance(x, y, xx, yy);
    xx = x;
    yy = y;
  }
  double res = dis / 50;
  cout << fixed << setprecision(9) << res * k << endl;
  return 0;
}
