#include <bits/stdc++.h>
using namespace std;
const int maxn = 103;
int n, k;
double x[maxn], y[maxn];
int main() {
  cin >> n >> k;
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
  }
  double dist = 0;
  for (int i = 0; i < n - 1; i++) {
    double t = sqrt((y[i + 1] - y[i]) * (y[i + 1] - y[i]) +
                    (x[i + 1] - x[i]) * (x[i + 1] - x[i]));
    dist += t;
  }
  double ans = dist * (double)k;
  ans /= 50.0;
  printf("%.6lf\n", ans);
}
