#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x1, y1, k, x, y;
  double dist = 0.0;
  cin >> n >> k;
  cin >> x1 >> y1;
  for (int i = 1; i < n; i++) {
    cin >> x >> y;
    dist += sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
    x1 = x;
    y1 = y;
  }
  cout << fixed << setprecision(15) << k * (dist / 50) << endl;
}
