#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  double n, k;
  cin >> n >> k;
  double a, b;
  cin >> a >> b;
  n--;
  double len = 0;
  while (n--) {
    double x, y;
    cin >> x >> y;
    len += ((double)sqrt(pow(x - a, 2) + pow(y - b, 2)));
    a = x;
    b = y;
  }
  len *= k;
  cout << fixed << setprecision(9) << len / (double)50 << "\n";
}
