#include <bits/stdc++.h>
using namespace std;
const int maxN = 100 * 10 + 100;
double n, d, ans, k;
pair<int, int> p[maxN];
int main() {
  cin >> n >> k;
  for (int i = 0; i < n; i++) cin >> p[i].first >> p[i].second;
  for (int i = 1; i < n; i++) {
    d = sqrt(pow((p[i].first - p[i - 1].first), 2) +
             pow((p[i].second - p[i - 1].second), 2));
    ans += d;
  }
  ans = ans * k;
  cout << fixed << setprecision(7) << ans / 50 << endl;
  return 0;
}
