#include <bits/stdc++.h>
using namespace std;
void init_code() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
}
int main() {
  init_code();
  int n, k;
  cin >> n >> k;
  int x[n], y[n];
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
  }
  double d = 0.0;
  for (int i = 0; i < n - 1; i++) {
    d += sqrt((x[i + 1] - x[i]) * (x[i + 1] - x[i]) +
              (y[i + 1] - y[i]) * (y[i + 1] - y[i]));
  }
  cout << fixed << setprecision(7);
  cout << d * k / 50.0 << "\n";
  return 0;
}
