#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  int n, k;
  cin >> n >> k;
  vector<int> x(n), y(n);
  double d = 0.000000000;
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
  }
  for (int i = 0; i + 1 < n; i++) {
    int dx = abs(x[i] - x[i + 1]);
    dx *= dx;
    int dy = abs(y[i] - y[i + 1]);
    dy *= dy;
    d += (double)(sqrt(dx + dy));
  }
  d *= k;
  cout << fixed << setprecision(10) << d / 50;
}
