#include <bits/stdc++.h>
using namespace std;
int main() {
  long double a[10000], b[10000], n, k, x = 0.0, y = 0.0, sum1 = 0.0, ans = 0.0,
                                        ans1 = 0.0;
  cin >> n >> k;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    cin >> b[i];
  }
  for (int i = 0; i < n - 1; i++) {
    x = (a[i] - a[i + 1]) * (a[i] - a[i + 1]);
    y = (b[i] - b[i + 1]) * (b[i] - b[i + 1]);
    ans1 = sqrt(x + y);
    sum1 += ans1;
  }
  sum1 *= k * 1.0;
  ans = sum1 / 50.0;
  cout << setprecision(10) << ans << endl;
  return 0;
}
