#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  double res = 0;
  double x1, y1, x2, y2;
  cin >> n >> k;
  for (int i = 0; i < n; ++i) {
    cin >> x2 >> y2;
    if (i) {
      res += sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
    }
    x1 = x2;
    y1 = y2;
  }
  res /= 50.0;
  res *= double(k);
  printf("%0.7f", res);
  return 0;
}
