#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, k;
  cin >> n >> k;
  vector<pair<long double, long double>> v;
  for (long long int i = 0; i < n; i++) {
    long double x, y;
    cin >> x >> y;
    v.push_back(make_pair(x, y));
  }
  long double sum = 0;
  for (long long int i = 1; i < v.size(); i++) {
    long double x1 = v[i - 1].first, y1 = v[i - 1].second, x2 = v[i].first,
                y2 = v[i].second;
    long double dis = sqrt(((x2 - x1) * (x2 - x1)) + ((y2 - y1) * (y2 - y1)));
    sum = sum + dis;
  }
  long double ans = ((1.0 / 50.0) * sum) * k;
  printf("%0.9Lf\n", ans);
}
