#include <bits/stdc++.h>
using namespace std;
double res, a, b;
int main() {
  int n, k;
  cin >> n >> k;
  vector<double> x(n), y(n);
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
    if (i) {
      a = x[i] - x[i - 1];
      b = y[i] - y[i - 1];
      res += sqrt((a * a) + (b * b));
    }
  }
  res /= 50;
  cout << setprecision(10) << res * k << endl;
}
