#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  long long int n, k, x, y, a, b;
  cin >> n >> k;
  vector<pair<long long int, long long int> > v;
  cin >> a >> b;
  v.push_back({a, b});
  double ans = 0;
  for (long long int i = 1; i < n; i++) {
    long long int x1, x2, y1, y2;
    cin >> x1 >> y1;
    v.push_back({x1, y1});
    x2 = v[i - 1].first, y2 = v[i - 1].second;
    long long int p = pow(abs(x2 - x1), 2);
    long long int q = pow(abs(y2 - y1), 2);
    double sum = p + q;
    double sum2 = sqrt(sum);
    ans = ans + sum2;
  }
  double ss = (double)ans / 50;
  cout << fixed << setprecision(10) << k * ss;
}
