#include <bits/stdc++.h>
using namespace std;
double getDist(double x1, double y1, double x2, double y2) {
  double x = (x1 - x2);
  double y = (y1 - y2);
  return sqrt(x * x + y * y);
}
int main() {
  int n, k;
  cin >> n >> k;
  double lastX, lastY;
  cin >> lastX >> lastY;
  double tDist = 0;
  for (int i = 1; i < n; i++) {
    double x, y;
    cin >> x >> y;
    tDist += getDist(lastX, lastY, x, y);
    lastX = x;
    lastY = y;
  }
  tDist *= k;
  tDist /= 50.f;
  cout << fixed << setprecision(7) << tDist << endl;
}
