#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n, k;
  cin >> n >> k;
  double x1, x2, y1, y2, ans = 0;
  cin >> x1 >> y1;
  for (int i = 0; i < n - 1; i++) {
    cin >> x2 >> y2;
    ans += pow(pow(x1 - x2, 2) + pow(y1 - y2, 2), 0.5);
    x1 = x2;
    y1 = y2;
  }
  ans = (ans / 50) * k;
  cout << setprecision(10) << ans;
  return 0;
}
