#include <bits/stdc++.h>
using namespace std;
template <typename T>
string tostr(const T& t) {
  ostringstream os;
  os << t;
  return os.str();
}
const int MAXN = 1002;
double dist(pair<double, double> a, pair<double, double> b) {
  return hypot(a.first - b.first, a.second - b.second);
}
pair<double, double> P[MAXN];
int main(int argc, char* argv[]) {
  double res = 0.0;
  int n, k;
  cin >> n >> k;
  for (int i = 0; i < n; ++i) cin >> P[i].first >> P[i].second;
  for (int i = 0; i < n - 1; ++i) res += dist(P[i], P[i + 1]) / 50.0;
  printf("%lf\n", k * res);
  return 0;
}
