#include <bits/stdc++.h>
using namespace std;
const double PI = 2 * acos(0.0);
const double eps = 1e-9;
const int N = 100;
int n, k, x[N], y[N];
int main() {
  cin >> n >> k;
  for (int i = 0; i < n; i++) cin >> x[i] >> y[i];
  double ans = 0.0;
  for (int i = 1; i < n; i++) {
    ans += hypot(x[i] - x[i - 1], y[i] - y[i - 1]);
  }
  ans *= k;
  cout << fixed << setprecision(10) << ans / 50 << endl;
  return 0;
}
