#include <bits/stdc++.h>
using namespace std;
const double PI = acos(-1);
void task() {
  int n, k, x, y, px, py;
  double ans = 0.0;
  cin >> n >> k;
  cin >> px >> py;
  n--;
  while (n--) {
    cin >> x >> y;
    ans += sqrt((x - px) * (x - px) + (y - py) * (y - py));
    px = x;
    py = y;
  }
  ans *= k;
  ans /= 50;
  printf("%.7lf\n", ans);
}
int main() {
  task();
  return 0;
}
