#include <bits/stdc++.h>
using namespace std;
int n, k;
pair<double, double> last, cur;
double len = 0.;
int main() {
  cin >> n >> k;
  cin >> last.first >> last.second;
  for (int i = 0; i < n - 1; ++i) {
    cin >> cur.first >> cur.second;
    len += sqrt((last.first - cur.first) * (last.first - cur.first) +
                (last.second - cur.second) * (last.second - cur.second));
    last = cur;
  }
  printf("%0.9lf\n", len * k / 50.);
  return 0;
}
