#include <bits/stdc++.h>
using namespace std;
double dist(double a, double b, double x, double y) {
  return sqrt(pow(a - x, 2) + pow(b - y, 2));
}
int main() {
  int n, k;
  cin >> n >> k;
  double l = 0.;
  double a, b;
  cin >> a >> b;
  double x, y;
  for (int i = 1; i < n; ++i) {
    cin >> x >> y;
    l += dist(a, b, x, y);
    a = x;
    b = y;
  }
  l *= k;
  cout.precision(12);
  cout << l / 50. << endl;
  return 0;
}
