#include <bits/stdc++.h>
using namespace std;
int x[105], y[105], i, n;
double len, ans, time1, k;
int main() {
  cin >> n >> k;
  for (i = 1; i <= n; i++) {
    cin >> x[i] >> y[i];
  }
  for (i = 1; i < n; i++) {
    len += sqrt(((x[i] - x[i + 1]) * (x[i] - x[i + 1])) +
                ((y[i] - y[i + 1]) * (y[i] - y[i + 1])));
  }
  ans = (len * k) / 50.0;
  cout << fixed << setprecision(6) << ans;
  return 0;
}
