#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int i;
  vector<int> x(n);
  vector<int> y(n);
  for (i = 0; i < n; i++) cin >> x[i] >> y[i];
  double sum = 0, res;
  for (i = 0; i < n - 1; i++)
    sum += sqrt((abs(x[i + 1] - x[i])) * (abs(x[i + 1] - x[i])) +
                (abs(y[i + 1] - y[i])) * (abs(y[i + 1] - y[i])));
  res = k * sum / 50;
  cout.precision(9);
  cout << res;
  return 0;
}
