#include <bits/stdc++.h>
using namespace std;
double length(int x1, int x2, int y1, int y2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
int main() {
  int n, k, x[128], y[128];
  cin >> n >> k;
  double s1, s2, len1, len2, len3, res = 0.0;
  for (int i = 0; i < n; ++i) {
    cin >> x[i] >> y[i];
    if (!i) continue;
    res += length(x[i], x[i - 1], y[i], y[i - 1]);
  }
  printf("%.8lf\n", res * k / 50.0);
  return 0;
}
