#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n, k;
  cin >> n >> k;
  double prev_x, prev_y, sum = 0;
  cin >> prev_x >> prev_y;
  for (int i = 1; i < n; i++) {
    double x, y;
    cin >> x >> y;
    sum += sqrt((pow(x - prev_x, 2) + pow(y - prev_y, 2)));
    prev_x = x;
    prev_y = y;
  }
  cout << fixed << setprecision(9);
  cout << (sum * k / 50);
  cout << endl;
  return 0;
}
