#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int x[n], y[n];
  for (int i = 0; i < n; i++) cin >> x[i] >> y[i];
  long double time = 0;
  for (int i = 0; i < n - 1; i++)
    time += sqrt((x[i] - x[i + 1]) * (x[i] - x[i + 1]) +
                 (y[i] - y[i + 1]) * (y[i] - y[i + 1]));
  time = time / 50;
  time *= k;
  cout << setprecision(7) << time;
  return 0;
}
