#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  vector<int> x(n), y(n);
  for (int i = 0; i < n; i++) cin >> x[i] >> y[i];
  double sum = 0;
  for (int i = 1; i < n; i++) {
    sum += hypot(x[i] - x[i - 1], y[i] - y[i - 1]);
  }
  sum = sum * 1.0 * k;
  printf("%.9lf\n", sum / 50.0);
}
