#include <bits/stdc++.h>
using namespace std;
int main() {
  float n, l = 100, m = 100, s = 0, x, y, k;
  cin >> n >> k;
  while (n--) {
    cin >> x >> y;
    if (l != 100 && m != 100) {
      s = s + sqrt((x - l) * (x - l) + (y - m) * (y - m));
    }
    l = x;
    m = y;
  }
  cout << fixed << setprecision(9) << float(s * k) / 50 << endl;
}
