#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, a, b, c, d;
  double s = 0;
  cin >> n >> k;
  cin >> a >> b;
  for (int i = 0; i < n - 1; i++) {
    cin >> c >> d;
    s += sqrt(pow(a - c, 2) + pow(b - d, 2));
    a = c;
    b = d;
  }
  cout << fixed << setprecision(9) << k * s / 50;
}
