#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  double res = 0.0;
  double x, y;
  cin >> x >> y;
  for (int i = 1; i < n; i++) {
    double cx, cy;
    cin >> cx >> cy;
    res += sqrt((cx - x) * (cx - x) + (cy - y) * (cy - y));
    x = cx;
    y = cy;
  }
  cout << setprecision(20) << endl;
  cout << res * k / 50.0 << endl;
  return 0;
}
