#include <bits/stdc++.h>
using namespace std;
std::clock_t __start;
double __duration;
void start_timer() { __start = std::clock(); }
void print_timer() {
  __duration = (std::clock() - __start) / (double)CLOCKS_PER_SEC;
  std::cout << "Duration (msec): " << __duration * 1000 << '\n';
}
template <class T>
T min_(T a, T b) {
  return (a < b ? a : b);
}
template <class T>
T max_(T a, T b) {
  return (a > b ? a : b);
}
double EPS = 1e-16;
bool eq_(const double& lhs, const double& rhs) {
  return (fabs(lhs - rhs) < EPS);
}
const int INF = int(2e9);
const long long INF_LL = LLONG_MAX;
const long long MOD = 1e9 + 7;
const int MAX_N = 1e6 + 5;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n, k;
  cin >> n >> k;
  double totald = 0.0;
  int lastx, lasty;
  cin >> lastx >> lasty;
  int x, y;
  for (int i = 1; i < n; ++i) {
    cin >> x >> y;
    totald +=
        sqrt(double((lastx - x) * (lastx - x) + (lasty - y) * (lasty - y)));
    lastx = x, lasty = y;
  }
  cout << std::fixed << std::setprecision(6) << k * totald / 50.0 << '\n';
  return 0;
}
