#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, p1, p2, dx, dy, td, dif1, dif2;
  float dis = 0.0, time, totaltime;
  cin >> n >> k;
  int x[n], y[n];
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
  }
  p1 = x[0], p2 = y[0];
  for (int i = 1; i < n; i++) {
    dif1 = (x[i] - p1);
    dx = (dif1 * dif1);
    p1 = x[i];
    dif2 = (y[i] - p2);
    dy = (dif2 * dif2);
    p2 = y[i];
    td = dx + dy;
    dis += sqrt(td);
  }
  time = (dis / 50);
  totaltime = (time * k);
  cout << fixed << setprecision(6) << totaltime << endl;
}
