#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, i, j;
  double distance;
  int a, b;
  cin >> n >> k;
  cin >> i >> j;
  while (--n) {
    cin >> a >> b;
    distance += sqrt((pow((i - a), 2)) + (pow((j - b), 2)));
    i = a;
    j = b;
  }
  cout << fixed << setprecision(8) << (distance * k / 50) << endl;
}
