#include <bits/stdc++.h>
using namespace std;
double ans = 0, x[2000], y[2000];
int n, k;
double dist(int i, int j) {
  return sqrt(((x[i] - x[j]) * (x[i] - x[j])) +
              ((y[i] - y[j]) * (y[i] - y[j])));
}
int main() {
  cin >> n >> k;
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
    if (i) ans += dist(i, i - 1);
  }
  ans = ans * k / 50;
  printf("%.11lf", ans);
  return 0;
}
