#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int x1, x2, y1, y2;
  double sum = 0;
  cin >> x2 >> y2;
  x1 = x2;
  y1 = y2;
  for (int i = 1; i < n; i++) {
    cin >> x2 >> y2;
    sum += sqrt(pow((x1 - x2), 2) + pow((y1 - y2), 2));
    x1 = x2;
    y1 = y2;
  }
  cout << fixed << setprecision(6) << sum * k / 50;
  return 0;
}
