#include <bits/stdc++.h>
using namespace std;
int power(int base, int pow) {
  if (pow == 0) return 1;
  return base * power(base, pow - 1);
}
int main() {
  int n, k;
  cin >> n >> k;
  double sum = 0;
  int x1, y1, x2, y2;
  cin >> x1 >> y1;
  n--;
  while (n--) {
    cin >> x2 >> y2;
    sum += sqrt(power(x1 - x2, 2) + power(y1 - y2, 2));
    x1 = x2;
    y1 = y2;
  }
  cout << fixed << setprecision(9) << sum * k / 50;
  return 0;
}
