#include <bits/stdc++.h>
using namespace std;
double dist(int x1, int y1, int x2, int y2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
int main() {
  int x, y, n, k;
  long double sum = 0;
  bool first = true;
  int lastX, lastY;
  cin >> n >> k;
  while (n--) {
    cin >> x >> y;
    if (first) {
      lastX = x;
      lastY = y;
      first = false;
      continue;
    }
    sum += dist(lastX, lastY, x, y);
    lastX = x;
    lastY = y;
  }
  cout << fixed << setprecision(9) << sum / 50 * k << endl;
  return 0;
}
