#include <bits/stdc++.h>
using namespace std;
struct point {
  int x = 0, y = 0;
} curr, prec;
int n, k;
double som = 0.0;
double dist(point a, point b) {
  return sqrt(double((b.x - a.x) * (b.x - a.x)) +
              double((b.y - a.y) * (b.y - a.y)));
}
int main() {
  cin >> n >> k;
  cin >> prec.x >> prec.y;
  for (int i = 1; i < n; prec.x = curr.x, prec.y = curr.y, i++) {
    cin >> curr.x >> curr.y;
    som += dist(prec, curr);
  }
  cout << setprecision(10) << (som * k) / 50;
  return 0;
}
